Evolution  of  the  Thermometer 


Dalence's  Thermometer  1688. 


Evolution  of  the 
Thermometer  ^  3> 


— BY — 

HENRY  CARRINGTON  BOLTON 

Author  of   Scientific  Correspondence  of 
Joseph  Priestley 


EASTON,    PA.: 

THE  CHEMICAL  PUBLISHING  Co. 
1900. 


COPYRIGHT,  1900,  BY  EDWARD  HART. 


CONTENTS. 


I.    The  Open  Air-thermometer  of  Galileo,     .     .     5 
II..   Therm oscopes  of  the  Accademia  del  Cimento,   25 

III.  Attempts  to  obtain  a    scale  from   Boyle  to 

Newton, 41 

IV.  Fahrenheit  and  the  first  reliable  Thermom- 

eters  61 

V.    Thermometers    of   Reaumur,    Celsius,     and 

others 79 

Table  of  Thirty-five  Thermometer  Scales,.     .     .     88 

Chronological  Epitome, 90 

Authorities, 92 

Index, 97 


91629 


EVOLUTION  OF  THE  THERMOMETER 


I.  THE  OPEN  AIR-THERMOMETER  OF 

GALILEO. 

Discoveries  and  inventions  are  sometimes  the 
product  of  the  genius  or  of  the  intelligent  in- 
dustry of  a  single  person  and  leave  his  hand 
in  a  perfect  state,  as  was  the  case  with  the  ba- 
rometer invented  by  Torricelli,  but  more  often 
the  seed  of  the  invention  is  planted  by  one, 
cultivated  by  others,  and  the  fruit  is  gathered 
only  after  slow  growth  by  some  one  who  ig- 
nores the  original  sower.  In  studying  the  ori- 
gin and  tracing  the  history  of  certain  discov- 
eries of  scientific  and  practical  value  one  is 
often  perplexed  by  encountering  several  claim- 
ants for  priority,  this  is  partly  due  to  the  cir- 
cumstance that  "  coincidence  of  independent 
thought  is  often  the  cause  of  two  or  more  per- 
sons reaching  the  same  result "  about  the  same 
time ;  and  partly  to  the  effort  of  each  nation 
to  secure  for  its  own  people  credit  and  renown. 
Again,  the  origin  of  a  prime  invention  is  some- 

i 


6      EVOLUTION  OF  THE  THERMOMETER, 

times  obscured  by  the  failure  of  the  discoverer 
to  claim  definitely  the  product  of  his  inspira- 
tion owing  to  the  fact  that  he  himself  failed  to 
appreciate  its  high  importance  and  its  utility. 
The  task  of  sketching  the  origin  of  the  ther- 
mometer is  fraught  with  similar  difficulties ; 
the  actual  inventor  is  known  only  at  second 
hand,  its  development  from  a  crude  toy  to  an 
instrument  of  precision  occupied  more  than  a 
century,  and  its  early  history  is  encumbered 
with  erroneous  statements  that  have  been  reit- 
erated with  such  dogmatism  that  they  have 
received  the  false  stamp  of  authority. 

One  of  the  most  persistent  of  these  errors  is 
the  assertion  that  the  thermometer  was  in- 
vented about  the  year  1608  by  a  Hollander 
named  Cornelius  Drebbel.  Wohlwill  and 
Burckhardt  have  shown  how  this  blunder 
originated.  In  1624  a  book  was  published  at 
Pont-a-Mousson,  entitled  u  La  Recreation  Math- 
ematicque,"  over  the  pen-name  A.  van  Etten, 
but  written  by  the  Jesuit  Father  Jean  Leure- 
chon,  in  which  the  author  describes  and  figures 
a  "  thermometer,  an  instrument  for  measuring 
degrees  of  heat  and  cold  that  are  in  the  air." 
The  book  was  popular,  passed  through  many 
editions  and  was  translated  into  several  Ian- 


GALILEO'S  OPEN  AIR-THERMOMETER.    7 

guages;  Casper  Ens  inserted  in  his  "  Thauma- 
turgus  mathematicus,"  published  at  Cologne 
in  1651,  a  translation  of  the  "  ;6th  Problem  " 
of  Leurechon,  containing  an  account  of  the 
thermometer,  and  added  to  the  word  "  instru- 
mentum"  the  adjective  "Drebbelianum." 
Reyer,  Sturm,  and  others  copied  the  phrase 
and  it  was  incorporated  in  an  article  published 
in  the  "Journal  des  Scavans,"  1678,  thus  be- 
coming a  part  of  authoritative  literature. 

Ten  years  later,  Dalence,  drawing  his  inspi- 
ration from  the  "Journal  des  S?avans,"  pub- 
lished an  attractive,  illustrated  volume  entitled 
"Traittez  des  barometres,  thermometres,  et 
notiometres,  ou  hygrometres,  Amsterdam, 
1688;"  in  this  he  wrote :  "The  thermometer 
was  invented  by  a  peasant  of  North  Holland, 
named  Drebbel,"  and  he  added  that  Drebbel 
was  "  called  to  the  court  of  King  James  where 
he  also  invented  the  microscope."  This  state- 
ment was  accepted  by  the  Dutch  savants  Boer- 
haave  and  Musschenbroek,  the  French  Abbe 
Nollet  and  others,  and  on  their  authority  has 
been  repeated  over  and  over  again,  so  that  un- 
til very  recently  all  encyclopedias,  dictionaries 
of  science  and  historical  essays  in  natural  philos- 
ophy adopted  without  reservation  the  phrase  : 


8      EVOLUTION  OF  THE  THERMOMETER. 

"the  thermometer  was  invented  by  Drebbel." 
And  yet  it  is  easy  to  show  that  the  Hollander 
had  no  part  in  the  invention  and  never  claimed 
it,  and  that  the  error  originated  in  the  misin- 
terpretation of  a  simple  experiment  described 
by  Drebbel  in  a  treatise  on  the  "  Elements." 

Cornelius  Drebbel,  born  in  Alkmaar,  Hol- 
land, 1572,  was  as  alchemist  who  claimed  to 
have  discovered  perpetual  motion,  and  ac- 
quired sufficient  reputation  for  learning  to  be 
invited  to  the  court  of  James  II,  King  of  Eng- 
land ;  to  him  he  dedicated  his  treatise  on  Pri~ 
mum  mobile  in  1607.  Later  in  life  he  visited 
Prague  where  Rudolph  had  gathered  famous 
alchemists,  astrologers,  and  magicians,  as  well 
as  more  reputable  astronomers,  artists,  anti- 
quarians, and  skilled  mechanics ;  Drebbel,  how- 
ever, was  unsuccessful  in  sustaining  his  claim 
to  the  discovery  of  perpetual  motion,  and  Em- 
peror Rudolph  threw  him  into  prison,  from 
which  he  was  released  'ere  long  by  the  death 
of  the  monarch,  in  1612. 

I  have  in  my  private  library  two  copies  of 
Drebbel's  rare  little  volume,  one  in  Dutch  bear- 
ing the  title :  "  Van  de  elementen  quinta  es- 
sentia  en  primum  mobile,  Amsterdam,  1709," 
and  with  a  second  title-page  having  the  words : 


GALILEO'S  OPEN  AIR-THERMOMETER.    9 

"Grondige  oplossinge  van  de  natuur  en  eyg- 
genschappenderelementen,  Amsterdam,  1732." 
The  other  copy  is  in  German  and  bears  the  date 
1715.  (Poggendorff,  the  German  historian  of 
physics,  admits  never  having  seen  an  edition 
of  this  treatise  by  Drebbel.) 

The  Dutch  version  contains  a  full-page  wood- 
cut representing  a  retort  hanging  by  a  chain 
from  a  hook  in  a  beam,  the  mouth  of  the  retort 
is  under  water  in  a  basin,  and  beneath  it  is  a 
fire ;  on  the  surface  of  the  water  are  seen  bub- 
bles of  air  issuing  from  the  retort ;  the  whole 
is  observed  by  two  men  in  out-door  costume. 
The  text  accompanying  this  picture,  when 
translated,  reads  as  follows  :  "Heat  makes  air 
and  water  subtle  and  light ;  cold,  as  the  oppo- 
site of  heat,  makes  them  smaller  and  presses 
them  together  and  condenses  all  the  air  that 
the  heat  had  made  to  rise,  as  may  be  clearly 
shown  when  a  glass  retort  is  hung  with  the 
mouth  in  a  bucket  of  water  and  fire  is  placed 
under  the  belly.  We  shall  then  see  that  as 
soon  as  the  air  in  the  glass  begins  to  get  hot, 
that  air  rises  out  of  the  mouth  of  the  retort, 
and  the  water  gets  full  of  bubbles,  and  this 
continues  so  long  as  the  air  gets  hotter ;  but  if 
the  firs  be  removed  from  beneath  the  retort 


io    EVOLUTION  OF  THE  THERMOMETER. 


and  the  air  begins  to  cool,  then  the  air  in  the 
retort  gets  thicker  and  heavier,  so  that  the  re- 
tort fills  with  water,  and  if  the  glass  was  made 
very  hot  the  water  will  completely  fill  it." 

This  simple  experiment  merely  shows  the 
expansion  of  air  by  heat  and  its  contraction 
by  cold,  and  there  is  no  question  whatever  of 
measuring  the  amount  of  heat;  besides,  Drebbel 
had  been  anticipated  by  Hero  of  Alexandria, 
who  described  essentially  the  same  phenomena 
1,750  years  before,  and  by  Drebbel's  contem- 
porary del  la  Porta. 

Giambattista  della  Porta  of  Naples,  the  pre- 
cocious author  of  "Magia  Naturalis"  (1558), 
is  sometimes  credited  with  the  invention  of  the 
thermometer,  owing  to  a  passage  in  his  book 
"  I  tre  libri  de  spiritali,"  published  at  Naples 
in  1606.  In  this  work  he  describes  an  experi- 
ment devised  to  measure  the  expansion  of  air 
when  heated  by  a  fire;  the  arrangement  de- 
scribed is  the  same  as  Drebbel's  retort  and 
basin,  but  the  cut  accompanying  the  text  shows 
an  inverted  matras  with  its  mouth  under  water; 
Porta  marked  on  the  tube  with  pen  and  ink 
the  highest  and  lowest  points  of  the  water- 
column,  but  he  does  not  seem  to  have  used  the 
instrument  as  a  heat-measurer. 


GALILEO'S  OPEN  AIR-THERMOMETER,     n 

The  word  "  thermoscope "  first  appears  in 
print  in  the  treatise  "  Sphsera  mundi,  seu  Cos- 
mographia  demonstrate  va,"  written  in  1617  by 
Giuseppe  Bianconi  and  printed  at  Bologna  in 
1620. 

The  word  "thermometer"  is  first  found  in 
Leurechon's  "  Recreation  mathematicque," 
(1624)  already  mentioned;  his  description  of 
the  instrument  is  the  earliest  that  gives  a  clear 
notion  of  those  in  current  use  at  the  beginning 
of  the  seventeenth  century,  and  is  markjed  by 
charming  simplicity  of  language. 

"It  is  an  instrument  of  glass  which  has  a 
little  bulb  above  and  a  long  neck  below,  or 
better  a  very  slender  tube,  and  it  ends  beneath 
in  a  vase  full  of  water,  or  it  is  curved  behind 
and  has  another  little  bulb  into  which  water 
or  any  other  liquid  may  be  poured  .  .  . 
It  is  used  thus :  Put  into  the  vase  below  some 
liquid  colored  blue,  or  red,  or  yellow,  or  other 
color  not  too  dark,  like  vinegar,  wine,  or  red- 
dened water,  or  aqua  fortis  which  has  been 
used  to  etch  copper.  Having  done  this,  I  say 
in  the  first  place  that  as  the  air  enclosed  in  the 
bulb  becomes  rarefied  or  condensed  the  water 
will  plainly  ascend  or  descend  in  the  tube ;, 
this  you  can  easily  test  by  carrying  the  instru- 


12    EVOLUTION  OF  THE  THERMOMETER. 


ment  from  a  very  hot  place  to  a  very  cold  one. 
But  without  disturbing  its  position,  if  you  lay 
your  hand  gently  on  the  upper  bulb,  it  is  so 
sensitive  and  the  air  is  so  susceptible  to  every 
impression,  that  you  will  instantly  see  the 
water  descend,  and  on  removing  the  hand  the 
water  will  return  to  its  place.  It  is  still  more 
sensitive  if  one  warms  the  bulb  with  his  breath, 
as  if  one  wished  to  speak  a  word  into  its  ear 
to  command  the  water  to  descend. 

"  The  reason  of  this  motion  is  that  the  air 
heated  in  the  tube  rarefies  and  dilates  and 
wishes  to  have  more  room,  and  therefore  presses 
upon  the  water  and  makes  it  descend.  On  the 
other  hand  when  the  air  is  cooled  and  con- 
denses it  begins  to  occupy  less  space  and  fear- 
ing to  leave  nothing  but  a  vacuum,  the  water 
ascends  at  once. 

u  I  say  in  the  second  place  that  by  this  means 
one  can  know  the  degrees  of  heat  and  of  cold 
that  are  in  the  air  at  each  hour  of  the  day,  the 
air  that  is  enclosed  in  the  bulb  rarefies  or  con- 
denses, ascends  or  descends.  Thus  you  see  in 
the  morning  the  water  stands  quite  high,  and 
it  descends  little  by  little  up  to  midday ;  to- 
wards vespers  it  remounts.  Thus  in  winter  it 
ascends  so  high  that  it  nearly  fills  the  tube  ; 


GALILEOS  OPEN  AIR-THERMOMETER.     13 


but  in  summer  it  descends  so  low  that  in  great 
heat  it  can  scarcely  be  seen  in  the  tube. 

"  Those  who  wish  to  determine  these  changes 
by  numbers  and  degrees  draw  a  line  all  along 
the  tube  and  divide  it  into  eight  degrees,  ac- 
cording to  the  philosophers,  or  into  four  de- 
grees according  to  the  physicians,  subdividing 
each  of  the  eight  spaces  into  eight  others  so  as 
to  make  sixty-four  little  ones.  And  by  this 
means  they  can  determine  to  what  degree  the 
water  ascends  in  the  morning,  at  midday  and 
at  every  hour.  Also  one  can  determine  how 
much  colder  one  day  is  than  another,  noting 
how  many  degrees  the  water  ascends  and  de- 
scends. One  can  compare  the  Q 
greatest  heat  and  cold  of  one 
year  with  those  of  another  year. 
One  can  ascertain  how  much 
hotter  one  room  is  than  an- 
other ;  one  can  maintain  a 
room  at  an  equal  temperature 
by  making  the  water  of  the 
thermometer  stand  always  at 
a  certain  degree.  One  can  test  also  the  intensity 
of  fevers  ;  in  short,  one  can  know  pretty  nearly 
to  what  extent  air  is  rarefied  in  the  greatest 
heat,  and  so  forth." 


Iveurechon's 
thermometers. 


14    EVOLUTION  OF  THE  THERMOMETER. 

This  interesting  account  is  accompanied  by 
two  illustrations,  copies  of  which  are  here 
given. 

Credit  for  the  invention  of  the  primitive 
form  of  the  thermometer  really  belongs  to  the 
famous  Italian  physicist  and  astronomer  Galileo 
Galilei,  notwithstanding  he  made  no  claim  to 
having  devised  the  instrument  and  his  extant 
writings  contain  only  a  casual  allusion  to  it. 
It  must  be  remembered,  however,  that  most  of 
the  manuscripts  of  Galileo  have  been  lost;  many 
were  consigned  to  the  flames  by  his  own  grand- 
son, Cosimo,  and  those  rescued  by  his  pupil, 
Viviani,  were  edited  only  in  part,  the  precious 
originals  being  scattered  by  the  ignorant  per- 
sons into  whose  possession  they  came.  In  the 
voluminous  correspondence  that  Galileo  car- 
ried on  with  contemporary  savants,  there  is 
abundant  evidence  that  he  was  the  inventor  of 
the  thermometer,  that  he  used  it  in  scientific 
research  and  labored  to  improve  its  efficiency, 
as  he  had  done  for  the  pendulum,  the  compass, 
the  telescope,  and  the  microscope. 

Viviani,  in  his  Life  of  Galileo,  published  in 
1718,  says  that  about  the  time  Galileo  took 
possession  of  the  chair  of  mathematics  in  Padua, 
which  was  at  the  end  of  the  year  1592,  he  in- 


GALILEO'S  OPEN  AIR-THERMOMETER.     15 

vented  the  thermometer,  a  glass  containing  air 
and  water  which  served  to  indicate  changes 
and  differences  in  temperature,  an  instrument 
afterwards  perfected  by  Ferdinand  II,  of  Tus- 
cany. This  assertion  is  confirmed  in  letters 
addressed  to  Galileo  by  his  friend  Francesco 
Sagredo,  of  Venice,  and  made  public  by  Nelli 
in  his  biography  of  Galileo.  The  first  of  these 
letters  is  dated  9  May,  1613.  Sagredo  writes: 
"The  instrument  for  measuring  heat,  which 
you  invented,  I  have  made  in  several  conve- 
nient styles,  so  that  the  difference  in  temperature 
between  one  place  and  another  can  be  deter- 
mined up  to  100  degrees."  And  he  then  gives 
examples  of  phenomena  that  he  has  examined 
by  the  aid  of  the  instrument. 

Two  years  later,  7  February,  1615,  Sagredo 
wrote  to  Galileo  more  fully :  u  The  use  of  the 
instrument  for  measuring  heat  and  cold  has 
been  improved  by  me,  and  I  think  there  is  op- 
portunity for  many  observations,  but  without 
your  cooperation  I  had  hardly  succeeded.  With 
this  instrument  I  see  clearly  that  the  water  of 
our  fountain  is  colder  in  winter  than  in  sum- 
mer, and  I  imagine  that  the  same  is  true  of 
springs  and  subterranean  places,  although  our 
feelings  seem  to  indicate  the  contrary. 


16    EVOLUTION  OF  THE  THERMOMETER. 

During  two  snowstorms  my  instrument  in  a 
room  here  showed  1 30  degrees  more  heat  than 
it  indicated  two  years  ago  during  extreme  cold; 
on  plunging  the  instrument  into  snow  it  indi- 
cated 30  degrees  less,  therefore  only  100,  but 
immersed  in  snow  and  salt,  it  showed  a  further 
100  degrees  less,  and  I  believe  in  reality  it 
marked  still  less  but  the  snow  and  salt  pre- 
vented it  being  seen  clearly.  In  the  greatest 
heat  of  summer  the  instrument  stood  at  360 
degrees,  and  hence  it  appears  that  snow  and 
salt  increase  the  cold  about  one-third  of  the 
difference  between  extreme  heat  of  summer 
and  extreme  cold  of  winter,  a  remarkable  fact 
the  reason  for  which  I  cannot  determine.  I 
shall  learn  with  pleasure  your  opinions,  espe- 
cially what  you  have  observed  of  the  cold  pro- 
duced by  saltpetre,  of  which  I  have  heard  many 
things,  but  have  not  personally  seen.  It  will 
be  difficult  to  send  the  instrument  direct  to 
you;  it  would  be  easier,  I  think,  to  have  one 
made  there." 

A  month  later  (15  March),  Sagredo  wrote  'to 
Galileo :  "I  have  daily  altered  and  improved 
the  instrument  for  measuring  temperature ;  if 
I  could  speak  with  you  in  person  I  could  tell 
you  from  the  beginning  the  whole  history  of 


GALILEO'S  OPEN  AIR-THERMOMETER.     17 

my  invention,  or  rather  of  my  improvements. 
But  since,  as  you  write  to  me,  and  as  I  stead- 
fastly believe,  you  are  the  first  to  discover  and 
make  the  instrument,  I  suppose  that  those 
made  by  you  and  your  excellent  workmen  are 
superior  to  my  own ;  therefore  I  beg  you  at 
the  first  opportunity  to  write  to  me  how  you 
have  them  made,  and  I  will  report  to  you  more 
or  less  of  what  is  happening  here." 

In  a  long  letter  to  Galileo,  written  1 1  April 
same  year,  Sagredo  mentions  the  use  of  wine 
as  well  as  of  water  in  the  thermometers,  alludes 
to  having  them  made  at  the  glass  works  in 
Murano,  near  Venice,  and  describes  the  con- 
struction of  the  best  and  most  perfect  of  his 
instruments.  This  was  made  of  a  glass  tube 
a  finger  wide  joined  to  a  bulb  having  a  capacity 
of  "three  or  four  drinking  glasses;"  having 
made  three  of  different  sizes  he  watched  their 
behavior  during  one  year,  sometimes  as  often 
as  eight  times  a  day,  and  he  expresses  wonder 
at  their  close  agreement  in  both  the  extremes 
of  cold  and  heat,  the  difference  between  them 
being  not  more  than  two  or  three  degrees.  He 
expresses  surprise  also  at  the  great  delicacy  of 
his  thermometers,  which  showed  a  difference 
of  temperature  when  moved  from  the  interior 


i8    EVOLUTION  OF  THE  THERMOMETER. 

of  a  room  to  the  open  door,  or  on  approaching 
them  to  a  person  or  a  lamp.  He  remarks  at 
the  same  time  that  instruments  made  of  thick 
and  of  thin  glass  do  not  change  with  equal  ra- 
pidity, the  thinnest  moving  the  quickest ;  he 
also  surmises  that  the  unequal  viscosity  of 
water  and  of  wine  makes  a  difference.  This 
interesting  letter  concludes  with  the  remark : 
"  Signer  Gageo  is  in  my  room  and  disturbs  me, 
and  I  do  not  want  him  to  see  what  I  am  wri- 
ting, so  my  letter  will  be  disconnected  for  my 
mind  is  occupied  in  several  ways." 

The  instrument  Galileo  used  is  described  in 
a  letter  written  by  Father  Castelli  to  Monsignor 
Cesarini,  dated  2oth  September,  1638,  in  which 
he  says  it  was  used  in  public  lectures  thirty- 
five  years  before.  Recounting  what  he  re- 
members seeing,  he  writes:  "Galileo  took  a 
glass  vessel  about  the  size  of  a  hen's  egg,  fitted 
to  a  tube  the  width  of  a  straw  and  about  two 
spans  long ;  he  heated  the  glass  bulb  in  his 
hands  and  turned  the  glass  upside  down  so  that 
the  tube  dipped  in  water  held  in  another  ves- 
sel ;  as  soon  as  the  ball  cooled  down  the  water 
rose  in  the  tube  to  the  height  of  a  span  above 
the  level  in  the  vessel ;  this  instrument  he  used 
to  investigate  degrees  of  heat  and  cold."  This 
lecture  experiment  dates  from  1603. 


GALILEOS  OPEN  AIR-THERMOMETER.     19 

In  Galileo's  extant  writings  there  is  only 
one  reference  to  the  thermometer  and  this  cor- 
responds in  time  with  the  letters  of  his  friend 
Sagredo.  In  this  fragment  Galileo  tries  to  ex- 
plain the  principle  of  the  thermometer;  he 
says  that  "when  the  air  in  the  bulb  contracts 
through  cold,  .the  wine  in  the  stem  rises  to 
take  the  place  of  the  void  thus  formed,  and 
when  the  air  is  warmed  it  is  rarefied  and  takes 
up  more  space  so  that  it  drives  out  and  presses 
down  the  wine  ;  "from  this,"  says  Galileo,  "  it 
follows  that  cold  is  nothing  but  absence  of 
heat." 

This  corres^Jmfenceand  this  fragment  es- 
tablish several^rrnigsT^Bt.  The  thermometer 
was  invented  by  Galileo  Galilei,  between  the 
years  1592  and  1597.  2nd.  The  instrument 
was  an  inverted  air  thermoscope  containing 
either  water  or  wine,  and  provided  with  a  scale 
of  degrees.  3rd.  By  its  use  Galileo  determined 
relative  temperatures  of  different  places  and  of 
the  same  place  at  different  seasons.  4th.  Gal- 
ileo made  thermometric  observations  of  freez- 
ing mixtures. 

Galileo's  method  of  graduating  the  stem  can- 
not be  ascertained,  and  was  undoubtedly  arbi- 
trary, Jjut  the  fact  that  he  cites  "degrees" 


20    EVOLUTION  OF  THE  THERMOMETER. 

prove  that  the  instrument  was  of  a  higher  type 
than  some  thermoscopes  of  even  a  later  date. 

Inverted  air  thermometers  of  this  construc- 
tion were,  of  course,  subject  to  changes  in  at- 
mospheric pressure,  and  were  properly  speak- 
ing "baro-thermoscopes,"  and  no  two  of  them 
were  comparable.  Sealed  thermometers  de- 
pending upon  the  expansion  of  liquids  and 
independent  of  air  pressure,  were  not  made 
until  fifty  years  later,  and  instruments  with 
fixed  points  capable  of  accurate  comparison 
were  not  devised  until  a  century  had  elapsed. 

The  savants  of  Italy  contemporary  with 
Galileo  naturally  becamejj^^nted  with  the 
great  discoveries  and^^m^^^sassociated  with 
his  name,  and  the  telescope  from  its  marvel- 
ous revelations  of  celestial  phenomena  con- 
tributed-th'e  most  to  magnify  his  reputation; 
the  great  importance  of  the  thermometer,  on 
the  other  hand,  was  appreciated  by  compara- 
tively few. 

One  of  the  colleagues  of  Galileo,  Sanctorius 
Sanctorius  Justipolitanus,  who  held  the  chair 
of  the  Theory  of  Medicine  at  the  University 
of  Padua  from  1611  to  1624,  applied  the  new 
instrument  to  physiological  researches  and  de- 
scribed the  results  in  several  of  his  publica- 


GALILEO'S  OPEN  AIR-THERMOMETER.     21 

tions.  The  earliest  of  these  references  occur 
in  his  "  Commentaries  on  the  Medical  Art  of 
Galen,"  published  in  1612,  but  written  a  year 
earlier,  for  the  "  license  "  is  dated  9  June  1611. 
Nelli  in  his  life  of  Galileo  cites  the  following 
passage :  "At  last  we  have  among  us  an  instru- 
ment by  which  with  a  bulb  we  measure  the 
withdrawal  of  heat  from  all  the  external  parts 
of  the  body  and  of  the  air ;  by  which  we  dis- 
cover, very  surely,  how  much  more  or  how 
much  less,  daily,  we  differ  from  the  normal 
[temperature]."  Burckhardt  cites  this  pas- 
sage at  second  hand,  transcribes  the  Latin 
erroneously,  and  says  the  sentence  does  not 
occur  in  the  copy  of  Sanctorius'  work  found 
in  the  public  library  at  Basel,  and  furthermore 
he  satisfied  himself  that  the  volume  contains 
no  reference  to  any  instrument  for  measuring 
heat;  both  these  statements  are  undoubtedly 
correct  so  far  as  concerns  the  copy  of  Sancto- 
rius which  Burckhardt  consulted,  but  I  have 
found  the  passage  in  the  copy  of  same  date 
preserved  in  the  United  States  Army  Medical 
Library,  Washington.  The  paragraph  occurs 
in  Part  III,  column  229,  and  this  third  part 
was  probably  wanting  in  the  volume  at  Basel. 
The -Historians  of  physics  seem  to  have  over- 


22    EVOLUTION  OF  THE  THERMOMETER. 

looked  another  passage  of  still  greater  interest 
which  I  discovered  in  the  copy  of  Sanctorius 
at  Washington.  Translated  it  reads  thus : 
"We  determine  the  temperature  by  means  of 
our  glass  instrument ;  we  ascertain  the  high 
and  the  low  (points)  after  this  manner :  we 
apply  snow  to  the  bulb  of  the  glass  instrument 
that  the  water  may  ascend  to  the  highest  point, 
then  we  approach  the  flame  of  a  candle  that 
the  water  may  descend  to  the  lowest  point." 

This  important  passage  shows  that  Sancto- 
rius appreciated  the  value  of  fixed  points  for 
graduation,  and  used  snow  and  the  heat  of  a 
candle  to  secure  extremes.  The  division  of  the 
stem  is  unknown,  but  he  mentions  in  one  place 
(to  be  mentioned  presently)  "  no  degrees." 

One  of  the  most  celebrated  books  of  Sanctorius 
is  his  "Medicina  statica,"  published  at  Venice 
in  1614,  and  which  passed  through  no  less  than 
eighteen  Latin  editions,  besides  two  French  ver- 
sions, four  English,  one  Italian,  and  one  German. 
In  the  first  edition  occur  the  following  inter- 
esting paragraphs  :  u  How  great  the  ponder- 
ousness  of  the  air  is,  may  in  the  first  place  be 
gathered  from  greater  or  less  weight  of  the 
dregs  of  alum  dried  before  in  the  sun  and  after- 
wards exposed  to  the  air  in  the  night  time. 


GALILEOS  OPEN  AIR-THERMOMETER.     23 


D 


Secondly,  from  our  feeling  a  greater  cold  than 
what  is  observable  in  the  weather-glass  (instru- 
mentum  temper atoruni).  For  the  moisture  or 
ponderousness  of  the  air  is  to  us  the  measure 
of  its  coldness.  Thirdly,  from  the  greater  or 
lesser  bending  of  a  very  thin  board,  especially 
if  it  be  of  a  pear  tree.  Fourthly, 
from  the  contraction  of  the  strings 
of  a  lute,  or  from  hemp."  (Section 
II,  Aphorism  IV,  English  trans- 
lation by  J.  D.,  London,  1678.) 

In  this  "aphorism"  Sanctorius 
mentions  three  hygroscopes  and 
one  thermoscope.  Parenthetic- 
ally, I  call  attention  to  the  use  of 
burnt  alum  and  of  a  balance  to  de- 
termine atmospheric  moisture 
quantitatively. 

The  thermoscope  used  by  Sanc- 
torius is  described  by  him  in  his 
"  Commentaries  on  the  first  sec- 
tion of  the  first  book  of  Avi- 
cenna,"  printed  at  Venice  in  1646. 
In  the  preface  to  this  the  author 
says  he  has  been  engaged  for 


A 


Sanctorius' 
thermometer. 


fifteen   years  in  preparing  descriptions  of  his 
instruments,  but  the  publication  has  been  de- 


24    EVOLUTION  OF  THE  THERMOMETER. 

layed  by  his  duties  as  lecturer  in  the  univer- 
sity. His  apparatus  resembled  closely  Galileo's^ 
being  a  glass  globe  attached  to  a  long  narrow 
tube  partially  filled  with  water,  which  stood  in 
a  small  open  vessel  of  water ;  when  the  air  in 
the  globe  is  warmed  the  water  in  the  tube 
sinks,  and  on  cooling  it  rises.  Sanctorius  says 
the  instrument  "was  used  by  Hero  for  other 
purposes,  but  I  have  applied  it  to  the  determi- 
nation of  the  warm  and  cold  temperature  of  the 
air  and  of  all  parts  of  the  body,  as  well  as  for 
testing  the  heat  of  persons  in  a  fever." 

Sanctorius  had  the  thermometer  made  in  a 
variety  of  forms  for  taking  the  temperature  of 
different  parts  of  the  body;  in  one  style  the 
bulb  was  inserted  in  the  mouth  of  the  patient 
and  the  long  S-shaped  tube  was  divided  into 
degrees ;  when  so  applied  the  bulb  was  allowed 
to  be  in  place  during  a  ten  pulse-beats."  Sanc- 
torius was  the  first  physician  to  recognize  that 
the  human  body  has  a  normal  temperature,  and 
to  determine  variations  from  it  as  an  aid  to  di- 
agnosis. He  also  attempted  to  ascertain  the 
heat  of  the  moon,  but  misinterpreted  his  re- 
sults ;  we  now  know  that  his  instruments  were 
not  sensitive  enough  for  the  purpose.  He  made 
an  experiment  to  measure  the  relation  between 


THERMOSCOPES  OF  THE  ITALIANS.      25 

the  heat  of  the  sun  and  of  the  moon,  and  re- 
corded that  in  sunlight  the  water  in  his  ther- 
mometer fell  "  no  degrees  in  two  pulse-beats." 
Before  dismissing  the  connection  of  Sancto- 
rius  with  the  thermometer  I  note  that  the  Ital- 
ian physician  nowhere  claims  to  have  invented 
it ;  on  the  contrary,  he  calls  it  in  his  u  Com- 
mentaries on  Galen  "  a  "  most  ancient  instru- 
ment." (P.  538,  edition  1612.)* 

II.  THERMOSCOPES  OF  THE  ACCADEMIA  DEL 
CIMENTO. 

Modifications  and  improvements  of  the  ther- 
moscope  were  probably  made  by  many  savants 
interested  in  their  use,  both  in  Italy,  the  birth- 
place of  the  instrument,  and  in  all  parts  of  Eu- 
rope to  which  the  knowledge  of  the  invention 
penetrated,  but  few  records  of  them  have  sur- 
vived. 

There  is  a  manuscript  preserved  in  the  library 
of  the  Arsenal,  Venice,  entitled  "  Matematica 
meravigliosa,"  written  by  Telioux,  a  Roman 
engineer,  in  1611,  that  is  said  by  the  historian 

*  Prof.  Cleveland  Abbe  suggests  that  this  instrument 
had  doubtless  been  used  to  illustrate  the  expansion  of 
air  by  heat  for  a  long  time  previous  to  Galileo,  who  simply 
added  a  scale  for  the  use  of  Sanctorius  so  that  the  physi- 
cian could  express  the  intensity  of  fevers. 


26    EVOLUTION  OF  THE  THERMOMETER. 

Libri  (Histoire  des  sciences  mathematiques  en 
Italic,  Vol.  IV,  p.  471,  notes),  to  describe  a 
thermoscope  independent  of  atmospheric  pres- 
sure. The  instrument  is  said  to  consist  of  a 
bulb  with  a  neck  a  foot  or  more  long,  nearly 
filled  with  water  into  which  a  smaller  bulb- 
tube  was  inverted  so  that  the  neck  was  beneath 
the  surface ;  Libri's  account  is  accompanied 
by  a  drawing  that  does  not  correspond  with 
the  description  and  is  obviously  incorrect  > 
whether  the  figure  is  from  Telioux'  manuscript 
does  not  appear,  but  if  it  is  of  the  date  1611,  it 
is  the  earliest  representation  of  a  thermometer 
with  scale  known  to  me.  The  scale  attached 
to  each  side  of  the  stem  is  divided  into  eight 
large  spaces,  and  each  space  into  sixty  smaller 
ones,  a  division  probably  suggested  by  the 
graduation  of  astronomical  instruments  into 
degrees  and  minutes. 

According  to  Poggendorff ,  Salomon  de  Caus, 
whose  name  is  associated  with  the  use  of  steam 
as  a  mechanical  power,  described  a  very  im- 
perfect thermometer  in  the  work  "  Raisons  des 
forces  mouvantes,"  published  at  Frankfurt  in 
1615. 

The  eminent  Englishman,  Lord  Chancellor 
Bacon,  is  sometimes  put  forward  as  the  inven- 


THERMOSCOPES  OF  THE  ITALIANS.      27 

tor  of  the  thermometer,  but  he  merely  alludes 
to  the  instrument  as  if  well  known.  In  the 
"  Novum  Organon,"  1620,  Bacon  describes  an 
inverted  u  heat-glass,"  styled  "  Vitrum  calen- 
dare,"  and  says  it  bore  "  attached  to  the  stem 
a  long  narrow  strip  of  paper  marked  off  with 
degrees  at  pleasure." 

Attempts  have  been  made  by  Italian  authors 
to  secure  the  credit  of  inventing  the  thermom- 
eter for  another  Englishman,  Robert  Fludd  de 
Fluctibus,  a  physician  and  mystic  whose  books 
show  more  erudition  than  common  sense.  The 
Jesuit  Franciscus  de  Lanis,  in  a  work  dated 
1670,  named  Fludd  as  the  original  inventor, 
and  Clemente,  in  his  life  of  Galileo,  1793,  has 
the  contemptible  effrontery  to  claim  that  Gal- 
ileo in  1603  used  an  instrument  made  by  Fludd. 
The  facts  are  that  about  the  year  1603  Fludd 
visited  many  countries  of  Europe,  including 
Italy,  where  he  may  well  have  seen  the  Gal- 
ileo thermoscope  known  to  savants  in  Padua. 
Twelve  years  after  Fludd's  return  to  England, 
in  1617,  he  published  a  work  (Utriusque 
cosmi  .  .  .  historia)  in  which  he  de- 
scribed an  experiment  chiefly  borrowed  from 
Hero,  of  Alexandria.  In  another  work  (Philo- 
sophia  Moysaica)  issued  in  1638,  a  year  after 


28    EVOLUTION  OF  THE  THERMOMETER. 

his  death,  Fludd  describes  a  "  Speculum  calen- 
darium,"  which  was  a  simple  thermoscope  of 
the  usual  pattern,  and  says  he  found  it  in  a 
manuscript  more  than  500  years  old.  This 
certainly  disposes  of  the  pretensions  of  those 
who  claim  Fludd  as  an  originator. 

The  instrument  figured  in  Fludd's  book  rep- 
resents the  usual  inverted  air  thermoscope  in 
a  basin  of  water,  the  stem  being  divided  into 
fourteen  degrees,  of  which  seven  are  below  and 
seven  above  a  central  line  named  u  sphaera 
aequalitis,"  a  curious  forerunner  of  our  modern 
zero  with  plus  and  minus  degrees. 

The  list  of  those  to  whom  the  invention  of 
the  thermometer  has  been  ascribed  should  in- 
clude the  Servite  monk  Fra  Paolo  Sarpi,  named 
by  Fulgenzio  for  the  honor;  "Father  Paul," 
as  he  is  called,  does  not  seem  to  have  used  the 
instrument  before  1617,  and  does  not  mention 
it  in  his  writings. 

Before  the  days  of  academies  of  science  and 
of  periodical  literature,  communication  between 
European  savants  was  maintained  by  personal 
visits  and  by  correspondence.  One  of  the  most 
active  intermediaries  between  scientists  in  the 
first  half  of  the  seventeenth  century  was  a 
French  theologian,  Father  Marin  Mersenne  ; 


THERMOSCOPES  OF  THE  ITALIANS.       29 

he  was  in  constant  communication  with  Gal- 
ileo, Descartes,  Gassendi,  Roberval,  Hobbes, 
and  others,  sending  them  news  of  discoveries 
and  inventions  in  exchange  for  similar  favors. 
Mersenne  was  also  an  experimenter,  repeating 
and  verifying  the  labors  of  others  and  thus 
familiarizing  himself  with  every  branch  of 
physical  science,  but  he  made  no  noteworthy 
discovery ;  he  was  the  originator  of  the  custom 
of  propounding  prize  questions,  a  scheme  for 
stimulating  scientific  work  afterwards  adopted 
by  certain  learned  societies.  His  "Recreations 
des  savans"  was  published  in  1634. 

There  lived  at  that  time  in  Southern  France 
an  obscure  physician  named  Jean  Rey,  who 
did  two  things  in  his  lifetime  that  ought  to 
have  brought  him  renown,  but  he  was  in  ad- 
vance of  the  age  and  his  discoveries  were  not 
appreciated  by  his  contemporaries.  Rey  ap- 
plied his  knowledge  of  chemistry  to  the  solu- 
tion of  the  much  vexed  problem  "  why  do  lead 
and  tin  increase  in  weight  when  calcined  ?" 
In  a  book  published  on  this  subject  in  1638, 
he  gave  the  correct  explanation,  recognizing 
that  the  metals  combined  with  a  constituent 
of  the  air,  and  anticipating  the  grand  truths 
that  made  Lavoisier  famous  150  years  later. 


30    EVOLUTION  OF  THE  THERMOMETER. 

Secondly,  Rey  was  the  first  to  make  use  of  the 
expansion  of  a  liquid  in  the  construction  of  a 
thermometer.  In  a  letter  written  to  Father 
Mersenne,  i  January,  1632,  he  said :  u  I  observe 
there  are  diverse  kinds  of  thermoscopes  and 
thermometers ;  what  you  tell  me  does  not 
agree  with  mine,  which  is  merely  a  small  round 
flask  having  a  very  long  slender  neck.  To 
make  use  of  it,  I  put  it  in  the  sun,  and  some- 
times in  the  hands  of  a  fever  patient,  having 
filled  it  quite  full  of  water  except  the  neck  ; 
the  heat  expanding  the  water  makes  it  ascend 
by  a  greater  or  less  amount  according  to  the 
great  or  little  heat." 

This  evidently  describes  a  water  thermom- 
eter, or  thermoscope,  and  so  far  embodied  a 
new  principle,  yet  it  was  still  influenced  by  the 
pressure  of  the  air.  The  instrument  did  not 
attract  much  attention. 

Mersenne  himself  devised  a  modification  of 
the  air  thermoscope  intended  to  increase  its 
delicacy,  and  described  it  in  a  work  published 
at  Paris  in  1644,  f°ur  years  before  his  death 
(Cogitata  physico-mathematica).  The  instru- 
ment consisted  of  a  narrow  tube  having  a  large 
bulb  at  one  end  and  a  small  one  at  the  other, 
the  latter  being  pierced  with  a  minute  hole ; 


THERMOSCOPES  OF  THE  ITALIANS,      31 

by  warming  gently  the  air  in  the  larger  bulb 
while  the  smaller  was  plunged  in 
water  and  then  removing  it,  a  few 
drops  of  the  liquid  rose  in  the  gradu- 
ated tube  forming  a  short  column  of 
water  that  served  as  an  indicator  of 
changes  of  temperature.  The  grad- 
uation of  the  stem  was 
peculiar;  it  was  divided 
into  eight  degrees  and 
these  were  numbered  on 
one  side  from  above  down 
ward,  and  on  the  other  thermometer 
in  reverse  order. 

In  1643,  the  learned  Jesuit  Atha- 
nasius  Kircher  published  a  quarto 
entitled :  "  Magnes,  sive  de  arte 
magnetica,"  in  which  he  mentions 
several  thermoscopes.  They  have 
the  usual  form  of  the  water-air 
instruments,  but  one  is  inverted 
making  it  convenient  for  testing 
the  temperature  of  liquids.  Kir- 
cher'explains  correctly  the  move- 

A.  Kircher's 

thermometer,  ment  ot  the  column  ot  water 
caused  by  the  expansion  of  the  air,  and  adds 
the  infecrument  indicates  the  goodness,  the  mild- 


32    EVOLUTION  OF  THE  THERMOMETER. 

ness,  and  salubrity  of  the  air  in  different  places, 
cultivated  fields,  plains  or  mountains,  as  well 
as  the  temperature  of  man  in  disease.  He 
mentions  a  thermoscope  containing  mercury, 
but  does  not  describe  its  construction  ;  the  text 
is  accompanied  by  the  figure  of  a  thermoscope 
of  which  the  stem  is  twisted  into  a  spiral  sev- 
eral feet  in  length.  No  reference  is  made  to  a 
scale.  (Magnes,  1643,  P-  5I5)« 

John  Baptist  van  Helmont,  a  physician  and 
chemist  of  Brussels,  used  in  1648  an  air-ther- 
mometer similar  in  design  to  that  of  Leure- 
chon,  except  that  the  stem  had  only  a  large 
drop  of  water,  as  in  that  of  Mersenne.  (Opera, 
1648,  p.  64.) 

A  most  important  and  radical  improvement 
in  thermometers  was  made  some  time  prior  to 
1654,  by  Ferdinand  II,  Grand  duke  of  Tuscany, 
the  liberal  patron  of  literature  and  art,  who  de- 
voted himself  also  to  practical  researches  in 
physical  science.  Ferdinand  made  a  thermom- 
eter of  the  usual  form,  filled  it  to  a  certain 
height  with  colored  alcohol  and  then  sealed  it 
hermetically  by  melting  the  glass  tip  ;*  the 

*  Rosenberger  in  his  "  Geschichte  der  Physik, " 
(Braunschweig,  1 882 , )  misunderstanding  the  alchem- 
ical expression  "closed  with  Hermes'  seal, "  says 
the  tube  was  closed  with  sealing-wax. 


THERMOSCOPES  OF  THE  ITALIANS.      33 

closed  instrument  was  then  graduated  by 
degrees  marked  on  the  stem. 

This  was  the  first  thermometer  independent 
of  atmospheric  pressure.  Torricelli,  it  will  be 
remembered,  had  shortly  before  invented  the 
barometer  and  demonstrated  the  weight  of  the 
atmosphere.  Tuscan  savants  and  Blaise  Pascal 
had  applied  it  to  the  measurement  of  eleva- 
tions. In  constructing  this  new  thermometer 
Ferdinand  probably  was  guided  by  an  experi- 
ment made  by  certain  Florentine  savants  to 
show  the  influence  of  atmospheric  pressure. 
The  latter  took  a  U-shaped  glass  tube  open  at 
both  ends,  on  one  arm  of  which  two  bulbs  were 
blown,  the  uppermost  ending  in  a  very  small 
open  point ;  at  the  foot  of  a  high  tower  the  U- 
tube  was  filled  to  a  certain  point  with  liquid 
that  reached  the  same  height  in  both  arms,  and 
the  open  point  was  then  closed  by  melting  the 
glass,  care  being  taken  not  to  warm  the  air  in 
the  bulbs.  The  whole  apparatus  was  then 
taken  to  the  top  of  the  tower  and  the  liquid 
was  seen  to  rise  in  the  open  arm  and  to  sink 
in  the  closed  arm  owing  to  diminished  pressure. 

Ferdinand  also  applied  the  principle  of  the 
Cartesian  divers  to  the  construction  of  a  ther- 
mometer, devising  an  entertaining  apparatus 


34    EVOLUTION  OF  THE  THERMOMETER. 

(glass  bulbs  floating  in  a  vessel  of  water),  that 
puzzled  many  philosophers ;  in  1649  ne  sent 
one  of  these  to  Athanasius  Kircher  and  one  to 
Raphael  Magiotti  at  Rome,  with  a  challenge 
to  explain  the  paradox,  and  both  the  Roman 
scientists  published  correct  solutions.  These 
instruments,  of  both  the  closed  and  the  open 
forms,  found  many  imitators,  Guericke,  Kir- 
cher, Dalence,  and  Pasumot,  but  are  not  suffi- 
ciently accurate  for  thermometrical  purposes. 
In  1657  Ferdinand  II,  of  Tuscany,  and  his 
brother,  Prince  Leopold  de  Medici,  made  a 
most  valuable  contribution  to  physical  science 
in  promoting  the  establishment  in  Florence  of 
a  society  destined  to  become  famous.  The  Ac- 
cademia  del  Cimento,  as  its  name  indicates, 
was  founded  for  the  express  purpose  of  ascer- 
taining by  experiment  the  facts  and  laws  of 
nature ;  it  numbered  only  nine  members,  most 
of  them  pupils  of  Galileo  (who  had  died  in 
1642),  besides  a  few  foreign  correspondents, 
and  they  devoted  themselves  to  experimental 
research  for  truth's  sake,  taking  as  their  motto 
"Provando  e  Riprovando."  They  did  not  even 
seek  personal  renown,  for  the  results  of  their 
investigations  were  published  in  the  name  of 
the  academy  only,  no  individual  being  men- 


THERMOSCOPES  OF  THE  ITALIANS.      35 

tioned.  The  meetings  were  held  in 
the  palace  of  Prince  Leopold,  who 
also  presided.  The  ecclesiastical 
authorities  did  not,  however,  ap- 
prove of  the  enterprise,  and  the 
same  power  that  persecuted  Galileo 
caused  the  academy  to  be  dissolved 
after  ten  years  of  useful  activity. 

The  results  or  the  members'  joint 
researches  were  published  in  1667 
in  a  volume  fascinating  to  the  his- 
torian of  science;  the  "  Saggi  di 
naturali  esperienze  fatte  nell'  Ac- 
cademia  del  Cimento,"  which  was 
translated  into  Latin  and  into  Eng- 
lish, the  latter  by  Richard  Waller, 
F.R.S.,  and  published  at  London 
in  1684  ;  this  edition  is  the  one  used 
in  these  chapters. 

Five  instruments  for  measuring 
heat  were  described  by  the  academy: 

I.  The  first  is  described  as  a  long 
tube  having  a  spherical    bulb   and 
closed  with  "Hermes'  seal"   at  the 
flame  of  a  lamp.     The  tube  is  filled    Florentine 
with  "spirit of  wine  up  to  a  certain  thermometer- 
mark  on  the  neck,  so  that  the  simple  cold  of 


36    EVOLUTION  OF  THE  THERMOMETER. 

snow  or  ice  externally  applied  may  not  be  able 
to  condense  it  below  the  20  degrees  of  the  tube, 
nor  on  the  contrary  the  greatest  vigor  of  the 
sun's  rays  at  midsummer  to  rarefy  it  above  80 
degrees."  The  tube  is  divided  into  ten  equal 
parts  with  compasses,  each  degree  being  marked 
with  white  enamel,  and  the  ten  intermediate 
divisions  with  green  glass  or  black  enamel. 
The  academy  preferred  alcohol  to  water  because 
it  is  "  sooner  sensible  of  the  least  change  of 
heat  and  cold,"  and  does  not  freeze  in  extreme 
cold.  The  alcohol  is  colored  with  solution  of 
kermes,  or  of  sanguis  draconis. 

II.  The  second  instrument  is  "but  a  copy 
of  the  former  in  little  " ;  the  first  being  divided 
into  100  degrees  and  the  second  into  50.  This 
comparison  is  then  anade  : 

No.  i.  No.  2. 

Degrees.  Degrees. 

Greatest  cold  of  winter          17  or  1 8         12  or  n 
Excessive  cold  one  year  8  6 

Midday  sun  80  40 

III.  The  third  thermometer  is  like  the  first 
but  much  larger,  its  length  being  200  degrees. 
Of  this  the  "  Saggi  "  say  :  u  We  can  lay  down 
no  certain  rule  to  make  it  practice,  often  trials 
being  the  only  way  to  effect  it ;  by  increasing 
and  diminishing  the  size  of  the  bulb  or  the 


THERMOSCOPES  OF  THE  ITALIANS.     37 

bore  of  the  cane,  or  the  quality  of  the  liquor, 
till  at  length  it  hits  it  right." 

IV.  The  fourth  thermometer  had  a  very  long 
tube  bent  in  the  form  of  a  spiral,  made  "  rather 
for  fancy  and  curiosity  to  see  the  liquor  run 
the  decimals  of  degrees  by  the  only  impulse  of 
a  warm  breath  than  for  any  accurate  deduc- 
tion."    This  instrument  is  styled  a  "  very  tick- 
lish thermometer." 

V.  The  fifth  instrument  was  a  wide  tube  of 
glass  nearly  filled  wilh  spirit  of  wine  in  which 
floated  several  little  glass  bulbs  adjusted  so  as 
to  sink  to  different  points  in  the  tube,  as  the 
temperature  of  the  liquid  rose.     This  instru- 
ment is  evidently  the  same  as  that  of  Ferdinand 
previously  noticed. 

Although  the  "Saggi  "  of  the  academy  were 
not  published  until  1667,  there  is  abundant 
proof  that  many  of  the  experiments  and  instru- 
ments therein  described  were  devised  many 
years  earlier,  some  of  them  even  before  the 
birth  of  the  academy.  It  is  certain  that  the 
principles  on  which  the  thermometers  were 
constructed  were  known  in  Florence  as  early 
as  1641,  sixteen  years  before  the  academy  was 
founded,  and  it  is  highly  probable  that  ther- 
mometers Nos.  i  and  2  were  made  from  the 

3 


38    EVOLUTION  OF  THE  THERMOMETER. 

designs  of  the  Grand  Duke  Ferdinand  himself, 
for  he  used  them  in  1 644  when  he  was  experi- 
menting on  the  artificial  hatching  of  eggs,  and 
in  meteorological  observations.  In  1646  Tor- 
ricelli  showed  thermometers  of  this  construc- 
tion to  the  distinguished  French  traveler, 
Monconys. 

The  members  of  the  academy  used  these 
thermometers,  especially  the  one  of  50  degrees 
which  they  found  the  most  convenient  and 
accurate,  in  a  variety  of  experiments  with 
freezing-mixtures  and  the  reflection  of  cold  by 
a  concave  glass.  The  thermometer  scales  can 
be  thus  compared : 

^ Academy  thermometers.    ^  Fahrenheit. 

73  37-5  96 

19  13-5  32 

—  8  —  8.5  o 

In  the  year  1829  a  number  of  Florentine 
thermometers  were  found  in  a  shop  in  Flor- 
ence by  Antinori,  and  Libri  ascertained  their 
scales  to  have  the  following  values :  (Ann. 
chim.,  45,  354). 

Flor.  C.  Fahr. 

13-5  o  32 

o  18.7  65.6 

50  55  131- 

The  academy's  thermometers  were  a  great 


7HERMOSCOPES  OF  7 HE  ITALIANS.      39 

advance  on  the  barothermoscopes  that  had 
preceded  them,  but  their  graduation  left  much 
to  be  desired  ;  those  of  different  lengths  had 
degrees  of  unequal  value,  and  individual  in- 
struments of  the  same  pattern  gave  results  only 
approximately  similar.  Their  agreement  de- 
pended on  the  skill  of  the  workmen,  who 
sought  to  get  comparable  thermometers  by 
taking  care  to  get  tubes  and  bulbs  equal  in 
size,  but  they  had  no  standard  of  graduation. 

Florentine  thermometers,  made  by  skilful 
workmen,  became  famous  throughout  Europe; 
together  with  Torricelli's  barometer  and  Ferdi- 
nand IPs  hygrometer,  they  were  used  at  me- 
teorological stations  established  by  the  Grand 
Duke,  and  conducted  in  Florence  by  Raineri, 
in  Pisa  by  Borelli,  as  well  as  in  Bologna,  Parma, 
Milan,  Warsaw,  and  Innsbruck ;  the  instru- 
ments were  observed  several  times  daily  and 
records  were  kept  with  great  fidelity.  One  of 
the  Italian  day-books  containing  sixteen  years' 
observations  was  examined  by  Libri  in  1830, 
and  he  obtained  evidence  that  the  climate  of 
Tuscany  had  not  materially  changed. 

The  meteorological  observations  made  in 
Florence  from  December  15,  1654,  to  March 
31,  1670,  were  published  entire  in  the 


40    EVOLUTION  OF  THE  THERMOMETER. 

"  Archivio  Meteorologico  Centrale  Italiano," 
Firenze,  1858,  introduction. 

The  thermometers  were  introduced  into 
France  by  the  way  of  Poland  ;  the  Grand  Duke 
Ferdinand  presented  some  philosophical  appa- 
ratus to  the  Envoy  of  the  Queen  of  Poland, 
and  her  secretary  sent  one  of  the  thermometers 
to  the  astronomer  Ismael  Boulliau  in  Paris, 
with  the  statement  that  Ferdinand  always  car- 
ried in  his  pocket  a  small  one  about  four  inches 
long. 

Meteorological  observations  were  carried  on 
in  Paris  from  1670  with  an  instrument  made 
for  De  la  Hire  by  Hubin.  The  scale  was  arbi- 
trary, but  the  thermometer  was  preserved  until 
those  with  reliable  scales  were  manufactured, 
and  its  values  determined  by  comparison,  thus 
permitting  the  records  to  be  adjusted. 

Florentine  thermometers  continued  to  be 
manufactured  for  general  use  in  the  eighteenth 
century;  G.  Reyger  records  that  Hanow,  in 
his  observations  of  the  weather  in  Danzig 
made  in  1741,  reported  temperatures  in  degrees 
of  the  "  usual  Florentine  scale,  the  o  being  in 
the  middle  of  the  tube,  indicating  temperate 
air,  or  45  Fahrenheit."  A.  Momber  also  states 
that  many  thermometers  made  in  Danzig  as 


SCALES  FROM  BOYLE  TO  NEWTON.      41 

late  as  the  middle  of  the  eighteenth  century 
had  three  scales,  Reaumur,  Fahrenheit,  and 
Florentine ;  one  of  these  is  in  the  possession  of 
the  Naturforschende  Gesellschaft  of  Danzig. 
Reaumur,  writing  in  1730,  speaks  of  Florentine 
thermometers  as  in  common  use. 

III.  ATTEMPTS  TO  OBTAIN  A  STANDARD 
SCALE  FROM  BOYLE  TO  NEWTON. 

Through  whom  knowledge  of  the  thermom- 
eters devised  by  the  Florentine  Academy 
reached  England  is  not  known,  but  it  has  been 
suggested  that  the  French  traveler  Monconys 
conveyed  it  to  the  Hon.  Robert  Boyle  on  the 
occasion  of  his  visit  to  London  in  1663,  and 
there  is  circumstantial  evidence  in  favor  of 
this  view.  Monconys  was  most  politely  re- 
ceived by  the  scholarly  Irishman  and  attended 
a  meeting  of  the  Royal  Society  on  the  3oth  of 
May ;  he  had  with  him  in  London  one  of  the 
new  instruments  and  made  an  entry  in  his 
diary  on  the  3ist  May  to  this  effect:  "The 
weather  was  cold  towards  evening  and  the  ther- 
mometer fell  to  6.5  degrees." 

While  the  Accademia  del  Cimento  was  busy 
experimenting  on  heat  and  cold,  magnetism 
and  acoustics,  and  trying  to  prove  the  "  non- 


42    EVOLUTION  OF  THE  THERMOMETER. 

existence  of  positive  levity,"  the  British  philoso- 
pher was  working  in  similar  fields ;  he  im- 
proved the  air-pump  (invented  in  1650  by  Otto 
de  Guericke),  devised  u  physico-mechanical  ex- 
periments touching  the  spring  of  the  air," 
discovered  the  fundamental  truth  known  as 
"  Boyle's  Law,"  invented  the  manometer,  and 
made  a  great  variety  of  observations  in  chem- 
istry and  physics  of  prime  importance.  All 
this  work  qualified  him  for  thermometrical 
studies,  and  it  is  said  that  he  constructed  a 
"  sealed  weather-glass  "  before  he  saw  the  Ital- 
ian instrument,  but  this  is  improbable. 

Boyle  graduated  the  stems  of  thermometers 
with  "  little  specks  of  amel  "  into  inches  and 
fractions  as  small  as  sixteenths ;  in  one  experi- 
ment he  found  that  "  sal-armoniac  "  dissolved 
in  water  "made  it  descend  to  2-11/16  inches  in 
a  quarter  of  an  hour.  He  observed  that  ther- 
mometer stems  were  not  sufficiently  even  and 
cylindrical,  being  often  widest  near  the  bulb, 
and  said  this  was  a  source  of  inaccuracy. 

Boyle  felt  the  need  of  a  standard  permitting 
comparison  of  effects  shown  by  different  ther- 
mometers, and  expressed  it  thus :  "  We  are 
greatly  at  a  loss  for  a  standard  whereby  to 
measure  cold.  The  common  instruments  show 


SCALES  FROM  BOYLE  TO  NEWTON.      43 

us  no  more  than  the  relative  coldness  of  the 
air,  but  leave  us  in  the  dark  as  to  the  positive 
degree  thereof;  whence  we  cannot  communi- 
cate the  idea  of  any  such  degree  to  another 
person.  For  not  only  the  several  differences 
of  this  quality  have  no  names  assigned  them, 
but  our  sense  of  feeling  cannot  therein  be  de- 
pended upon  ;  and  thermometers  are  such  very 
variable  things  that  it  seems  morally  impossi- 
ble from  them  to  settle  such  a  measure  of  cold- 
ness as  we  have  of  time,  distance,  weight,  etc." 


Boyle  endeavored  to  overcome  this  difficulty  ; 
believing  that  the  melting-point  of  ice  varied 
with  geographical  latitude,  he  proposed  using 
the  oil  of  aniseed  for  getting  a  fixed  point, 
placing  it  around  the  bulb  of  an  alcohol  ther- 
mometer, allowing  the  oil  to  freeze  and  mark- 
ing the  height  of  the  spirit  of  wine  in  the  bulb 
"when  the  oil  begins  to  curdle." 

This  scheme  for  getting  a  fixed  point  has 
been  wholly  misunderstood  by  some  historians 
who  state  that  Boyle  filled  his  thermometers 
with  aniseed.  oil  ! 

While  Boyle  tried  to  secure  one  fixed  point 
he  overlooked  the  advantages  of  having  two  ; 
he  strove  to  compute  the  absolute  expansion 


44    EVOLUTION  OF  THE  THERMOMETER. 

of  alcohol  and  to  divide  the  scale  into  ten 
thousandths,  or  some  aliquot  part  of  the  total 
expansion. 

Strange  notions  of  natural  phenomena  were 
current  in  Boyle's  day  and  the  "Father  of 
Chemistry  "  was  not  above  crediting  absurdi- 
ties ;  he  quoted  Orthelius  who  wrote:  "The 
liquor  distilled  from  the  ore  of  magnesia,  or  of 
bismuth,  will  swell  considerably  in  the  glass 
it  is  kept  in  at  the  full  moon,  and  subside  at 
the  new." 

Contemporary  with  Boyle,  another  distin- 
guished British  philosopher  was  occupied  with 
improvements  in  thermometers.  Robert  Hooke, 
afterwards  secretary  of  the  Royal  Society,  pub- 
lished in  1664  his  "  Micrographia ;"  in  this 
work  he  says  :  "I  have  brought  sealed  ther- 
mometers to  a  great  certainty  and  tenderness, 
for  I  have  made  some  with  stems  above  four 
feet  long'  in  which  the  expanding  liquor  would 
so  far  vary  as  to  be  very  neer  the  top  in  the 
heat  of  summer  and  preety  neer  the  bottom  at 
the  coldest  time  of  winter."  Hooke  filled  his 
thermometers  with  "  best  rectified  spirit  of 
wine  highly  ting'd  with  the  lovely  colour  of 
cochineal."  To  graduate  the  stem  he  placed 
zero  at  the  point  which  the  liquid  stood  when 


SCALES  FROM  BOYLE  TO  NEWTON.       45 

the  bulb  was  placed  in  freezing  distilled  water  ; 
he  then  marked  the  divisions  above  and  below 
"according  to  the  degrees  of  expansion  or  con- 
traction of  the  liquor  in  proportion  to  the  bulk 
it  had  when  it  indur'd  the  freezing  cold." 

Edmund  Halley,  writing  in  1700,  said  that 
Hooke  exhibited  at  Gresham  College,  2nd  Jan- 
uary, 1667-8,  a  combination  of  barometer  and 
thermometer  in  separate  tubes,  the  freezing- 
point  of  water  being  equal  to  zero,  and  the 
stem  being  graduated  from  — 70  to  +130. 

Hooke  made  an  important  step  in  advance 
when  he  took  the  freezing-point  of  water  as  a 
fixed  point  in  the  scale,  but  the  statement  made 
by  Brewster  that  in  1684  Hooke  proposed  the 
boiling-point  as  a  second  fixed  point  has  been 
examined  by  Poggendorfl  and  not  verified.  The 
claim  has  been  made  that  the  two  fiduciary 
points  were  first  proposed  by  the  Dutch  mathe- 
matician Christian  Huyghens,  in  a  Letter  dated 
and  January,  1665,  addressed  to  Robert  Moray. 
(A.  Member,  Schr.  naturf.  Gesch.  Danzig,  N. 
F.  VII,  108.)  Huyghens  wrote:  "It  would 
be  well  to  have  a  universal  and  determinate 
standard  for  heat  and  cold,  securing  a  definite 
proportion  between  the  capacity  of  the  bulb 
and  tiie  tube,  and  then  taking  for  the  com- 


46    EVOLUTION  OF  THE  THERMOMETER. 

mencement  the  degree  of  cold  at  which  water 
begins  to  freeze,  or  better  the  temperature  of 
boiling  water,  so  that  without  sending  a  ther- 
mometer to  a  distance,  one  could  communicate 
the  degrees  of  heat  or  of  cold  found  in  experi- 
ments and  record  them  for  the  use  of  posterity." 
In  this  passage  Huyghens  does  indeed  sug- 
gest the  two  phenomena  for  fixing  a  standard, 
but  only  as  alternatives,  and  he  seems  to  have 
had  no  idea  of  dividing  the  space  between  them. 
The  proposition  to  divide  into  equal  parts  the 
interval  between  two  points  to  be  ascertained 
by  experiment  was  made  four  years  later  by 
Honore  Fabri,  a  Jesuit  of  French  birth,  who 
had  been  one  of  the  corresponding  members  of 
the  Accademia  del  Cimento.  In  his  volumi- 
nous work  on  physics  published  in  1669,  he 
describes  an  experiment  with  a  Florentine  ther- 
mometer for  the  purpose  of  constructing  such 
a  scale ;  he  applied  snow  in  very  cold  weather 
to  the  bulb  and  marked  the  point  at  which  the 
liquid  stood,  then  he  marked  the  position  of  the 
liquid  at  the  highest  heat  of  summer  and  di- 
vided the  line  drawn  between  these  points  into 
eight  equal  parts.  As  we  now  know,  the  higher 
fixed  point  was  ill-chosen,  but  the  method  was 
correct  in  principle,  though  not  adopted  until 


SCALES  FROM  BOYLE  TO  NEWTON.      47 

long  after.  Meteorological  observations  were 
made  with  Hooke's  thermometers  by  John 
Wallis,  professor  of  mathematics  in  Oxford 
University,  and  he  recorded  in  a  certain  paper 
published  in  the  Philosophical  Transactions 
for  1669,  (p.  113),  that  the  "liquor"  stood  at 
three  and  one-half  inches  on  December  26, 
1669,  and  at  seven  inches  in  "  brisk  frosts." 

Several  novel  forms  of  thermometers  were 
constructed  about  1660-62  by  the  accomplished 
experimenter  in  physics,  Otto  de  Guericke, 
Burgomaster  of  Magdeburg ;  they  all  bore  im- 
press of  his  genius,  and  one  of  them  was,  and 
still  remains,  unique  in  many  particulars.  It 
was  gigantic  in  size  being  above  twenty  feet 
long,  gorgeous  with  blue  paint  and  gilt  stars, 
and  decorated  with  the  image  of  a  winged 
angel  whose  outstretched  arm  pointed  to  the 
temperature  at  every  moment.  For  conve- 
nience the  immense  air-thermoscope  was  fast- 
ened to  the  wall  of  a  house  on  the  shady  side ; 
it  was  renowned  for  its  power  of  showing  u  the 
coldest  and  hottest  weather  throughout  an  en. 
tire  year." 

The  instrument  consisted  of  a  large  ^copper 
globe  joined  to  a  long  tube  one  inch  wide,  of 
the  saine  metal ;  the  tube  was  bent  upon  itself 


48    EVOLUTION  OF  THE  THERMOMETER, 


Guericke'sthermomet'r. 


so  as  to  form  a  very  narrow 
U,  in  which  was  placed  a 
certain  amount  of  alcohol. 
The  shorter  arm  of  the  U  was 
open  at  the  top  ;  on  the  liquid 
within  it  floated  a  tiny  in- 
verted cup  of  brass  foil  to 
which  a  cord  was  attached 
that  passed  around  a  wheel, 
hung  upon  the  underside  of 
the  globe,  and  carried  at  the 
other  end  a  little  figure  of  an 
angel  pointing  to  the  scale  on 
the  tube;  the  tube  was  con- 
cealed from  the  observer  by 
a  wooden  case,  and  the  image 
hung  without.  A  valve  at 
one  side  of  the  large  copper 
sphere  permitted  enough  air 
to  be  withdrawn  by  means 
of  the  air-pump,  to  adjust  the 
height  of  the  image,  which 
hung  about  half  way  up  the. 
tube.  On  the  fifteen-foot 
scale  were  the  words  :  u  Mag- 


subfrigidus,    aer  temperatus,   aer    subcalidus, 


SCALES  FROM  BOYLE  TO  NEWTON.      49 

aer  calidus,  magnus  calor ;"  and  the  large 
sphere  above  the  tube  was  inscribed  "Mobile 
perpetuum." 

De  Guericke  constructed  a  barometer  on 
similar  lines,  and  gave  it  the  legend  "  Semper 
vivum ;"  he  described  it  in  a  letter  to  G.  Schott, 
dated  30  December,  1661. 

Still  more  remarkable  was  the  self-register- 
ing meteorological  apparatus  devised  by  the 
great  German  physicist ;  it  recorded  every  hour 
the  change  in  temperature,  direction  of  the 
wind,  the  rainfall,  and  amount  of  snow  or  hail. 
Monconys  describes  this  briefly,  with  a  diagram 
showing  the  arrangement,  in  his  Journal  des 
Voyages  (Vol.  Ill,  1663). 

The  differential  thermometer  was  invented 
by  Gaspar  Schott,  as  early  as  1657  (Mechan. 
hydraul-pneumat.  II,  231),  and  afterwards  im- 
proved by  Joh.  Christ.  Sturm,  Professor  in 
Altorf,  Bavaria,  in  1676.  It  was  a  U-tube 
with  arms  of  uneven  length,  both  tubes  being 
closed  ;  Sturm  explained  its  action  quite  cor- 
rectly. 

In  the  latter  part  of  the  seventeenth  century 
references  in  scientific  literature  to  the  con- 
struction and  use  of  the  ordinary  thermoscopes 
multiplied ;  Le  Febure  in  his  admirable  treat- 


50    EVOLUTION  OF  THE  THERMOME7ER. 

ise  on  chemistry  (1669),  mentions  the  ther- 
mometer as  a  well-known  instrument,  and  Ga- 
briel Clauder  in  the  "  Miscellanea  ctiriosa  Acad. 
nat.  curiosa"  (Dec.  2,  Anno  6,  p.  351,  1687), 
describes  a  "  thermoscopium  noviter  inven- 
tum  "  adapted  to  immersion  in  liquids. 

There  was  published  at  Amsterdam,  in  1688, 
an  illustrated  work  entirely  devoted  to  barom- 
eters, thermometers,  and  hygrometers,  written 
by  Dalence,  who  concealed  his  name  under  the 

initial  D .  I  have  already  referred  to  this 

interesting  book  in  connection  with  the  Dreb- 
bel  myth,  but  it  deserves  emphasizing,  for  it 
contains  an  imperfect  summary  of  thermomet- 
rical  knowledge  up  to  that  date ;  to  avoid  repe- 
tition, however,  I  shall  only  notice  items  not 
previously  given  here. 

Dalence  describes  the  Italian  thermoscope 
as  having  a  bulb  the  size  of  a  pigeon  egg  and 
a  tube  as  big  as  a  quill  pen*;  he  suggests  the 
use  of  a  mixture  of  three  parts  of  water  with 
one  of  aqua  fortis  to  prevent  the  liquid  freez- 
ing, and  a  flattened  bulb  to  permit  heat,  or 
cold,  more  readily  to  penetrate  the  centre  of 
the  liquid.  He  proposed,  also,  that  two  points 
should  be  marked  on  the  scale,  the  freezing- 
point  of  water,  to  be  marked  u  cold,"  and  the 


SCALES  FROM  BOYLE  TO  NEWTON.      51 

melting-point  of  butter ;  the  space  between 
them  to  be  divided  equally  and  the  centre  to 
be  marked  "temperate."  Then  each  space 
above  and  below  "temperate"  to  be  divided 
into  ten  equal  degrees,  four  additional  degrees 
to  be  placed  above  the  melting-point  of  butter 
and  four  below  the  freezing-point  of  water, 
making  a  scale  of  thirty  degrees  in  all. 

Dal.  Fahr. 

Melting  butter    .         .         .         10  86° 

Medium  o 

Freezing  temperature          .      — 10  32° 

He  further  proposed  another  standard  scale, 
the  fixed  points  to  be  the  temperature  of  a  cel- 
lar and  of  ice,  the  space  between  to  be  divided 
into  fifteen  degrees ;  and  he  added:  "all  ther- 
mometers made  by  the  latter  method  are  com- 
parable." To  make  instruments  easy  of  trans- 
portation, and  for  fancy,  the  stems  were  bent 
into  circular,  oval,  spiral,  triangular,  and  stel- 
late shapes,  and  Dalence  gives  figures  of  each. 
He  also  described  the  floating  glass  bulbs  of. 
Kircher,  and  made  them  in  the  shape  of  turtles 
to  apply  to  the  arms  and  body  of  feverish  per- 
sons. "Some  curieux"  he  says,  "use  mer- 
cury in  thermometers,"  but  the  instrument  he 
writes  of  was  an  air-thermoscope  and  the  fluid 
metal  was  not  employed  on  account  of  its  prop- 


52     EVOLUTION  OF  THE  THERMOMETER. 

erty  of  expansion.  Dalence  praised  the  skill  of 
Sieur  Hubin,  glass-blower,  whose  address  was 
Rue  St.  Martin,  Paris,  and  says  his  success  is 
due  to  the  fact  that  "he  knows  the  reasons  for 
that  which  he  does." 

The  sections  in  Dalence's  work  on  the  ba- 
rometer and  hygrometer  are  interesting  from 
the  historical  point  of  view,  but  do  not  fall 
within  the  province  of  these  chapters. 

Dalence  seldom  gives  credit  to  individuals 
for  their  shares  in  the  development  of  the  in- 
struments he  describes,  and  it  is  difficult  to 
determine  how  many  of  the  improvements  men- 
tioned by  him  were  original  with  him,  proba- 
bly but  few. 

Mention  may  be  here  made  of  a  complicated 
thermometer  constructed  by  the  expert  Pari- 
sian glass-blower  Hubin,  although  it  was  not 
described  in  print  until  1725  (Reyher,  Pneu- 
matica).  Two  bulbed  tubes  were  united  at 
a  reservoir,  and  bent  in  the  shape  of  an  U ; 
both  tubes  were  closed  so  that  the  apparatus 
was  independent  of  air-pressure.  The  shorter 
arm  of  the  U  was  filled  with  mercury  up  to  the 
centre  of  the  reservoir,  the  longer  arm  half 
filled  with  water,  the  remaining  half,  inclu- 
ding the  large  bulb,  containing  air.  When  the 


SCALES  FROM  BOYLE  TO  NEWTON.      53 

air  in  the  bulb  expanded,  it  pressed  upon  the 
column  of  water  which  in  turn  forced  the  mer- 
cury up  the  shorter  and  wider  tube.  Hubin 
claimed  for  this  instrument  greater  delicacy 
than  the  Florentine  in  the  proportion  of  216 
to  4,  as  determined  by  experiment. 

The  question,  who  first  used  quicksilver  as 
the  dilating  liquid  in  thermometers,  is  appar- 
ently a  simple  one,  to  be  easily  answered,  but 
like  many  other  questions  of  priority  in  the 
history  of  the  thermometer,  many  claims  have 
been  advanced  and  the  problem  requires  exam- 
ination ;  no  less  than  ten  names  are  mentioned 
by  different  authorities  as  inventors  of  mercury 
thermometers.  Thermometers  containing  mer- 
cury were  indeed  made  at  an  early  date,  but 
the  liquid  metal  was  only  an  accessory  to  the 
air-thermoscope  and  was  not  used  as  a  heat- 
measurer. 

Athanasius  Kircher,  in  1643,  mentions  a 
thermoscope  containing  mercury,  but  does  not 
describe  the  function  of  the  liquid  metal.  The 
Accademia  del  Cimento,  as  related  in  the  diary 
of  the  society,  made  mercury  thermometers  in 
1657,  compared  them  with  water-thermometers 
of  the  same  size,  and  observed  that  the  former 
fell  and  rose  more  quickly  than  the  latter  when 
4 


54    EVOLUTION  OF  THE  THERMOMETER. 

affected  by  changes  of  temperature,  although 
the  total  amount  was  less;  but  this  important 
fact  lay  dormant  and  unused. 

Mercury  thermometers  were  also  known  in 
Paris ;  Ismael  Boulliau  is  said  to  have  made  them 
in  1659;  and  a  letter  dated  28th  May,  1684, 
written  in  Paris  to  the  Royal  Society,  London, 
by  Mr.  Musgrave,  describes  one  three  inches 
long  and  five  lines  in  diameter,  that  was  used 
lor  taking  the  temperature  of  fever  patients. 

Christian  Huyghens,  in  1665,  and  Dalence, 
in  1668,  are  also  credited  with  the  invention 
of  mercury  thermometers.  In  the  same  year 
that  Dalence's  book  appeared,  Edmund  Halley, 
the  eminent  English  mathematician  and  astron- 
omer, was  studying  experimentally  the  rela- 
tive expansion  of  water,  alcohol  and  mercury, 
and  he  stated  that  mercury  would  make  a  good 
thermometrical  liquid  if  its  coefficient  of  ex- 
pansion was  greater ;  he  did  not  actually  rec- 
ommend the  liquid  metal,  although  he  per- 
ceived that  its  expansion  was  large  enough  to 
influence  the  readings  of  the  barometer.  He 
observed  that  mercury  heated  in  boiling  water 
ceased  to  expand  on  long  continuing  the  oper- 
ation, and  according  to  Momber  he  proposed 
taking  the  boiling-point  of  water  as  a  fixed 


SCALES  FROM  BOYLE  TO  NEWTON.       55 

point,  but  Poggendorff  says  he  made  no  appli- 
cation of  this  fact  to  thermometry.  Halley 
thought  that  "spirit  of  wine"  lost  part  of 
its  expansive  force  by  long  keeping,  yet  he 
proposed  the  boiling-point  of  alcohol  as  a  limit 
to  thermometrical  scales.  The  English  scien- 
tist felt  the  need  of  a  reliable  thermometer  scale 
and  expressed  himself  in  somewhat  the  same 
way  as  his  countryman  Boyle  had  done,  four- 
teen years  before  :  "I  cannot  learn  that  any 
thermometer  of  either  sort  was  ever  made  or 
adjusted  so  as  it  might  be  concluded  what  the 
degrees  or  divisions  of  the  said  instrument  did 
mean;  neither  were  any  thermometers  ever 
otherwise  graduated  but  by  standards  kept  by 
each  particular  workman  without  any  agree- 
ment or  reference  to  one  another.  So  that 
whenever  observations  of  a  thermometer  are 
made  by  any  curious  person  to  signify  the  de- 
gree of  heat  in  the  air  or  other  thing  they  can- 
not be  understood,  unless  by  those  who  have 
by  them  thermometers  of  the  same  make  and 
adjustment." 

Halley  regarded  the  freezing-points  of  aniseed 
oil,  and  of  water,  as  unreliable,  and  preferred 
as  a  starting  point  the  temperature  of  a  deep 
cellar* the  constancy  of  which  had  been  de- 


56    EVOLUTION  OF  THE  THERMOMETER. 

monstrated  by  De  la  Hire  in  the  crypt  of  the 
Paris  observatory. 

Christian  Wolf,  of  Halle,  and  Olof  Romer, 
of  Copenhagen,  both  in  1709,  are  also  named 
as  the  first  to  use  mercury  as  a  heat  measuring 
liquid,  but  in  spite  of  these  many  claimants 
the  fact  remains  that  Fahrenheit,  in  1714,  was 
incontestably  the  first  to  construct  mercury 
thermometers  having  reliable  scales.  But  this 
anticipates. 

The  need  of  a  standard  scale,  easily  made 
and  based  on  constant  phenomena  that  can  be 
reproduced  at  will,  was  felt  by  all  who  used 
thermometers,  and  an  important  practical  pro- 
posal to  secure  this  desideratum  was  made  in 
1694  by  Carlo  Renaldini,  a  former  member  of 
the  Accademia  del  Cimento.  and  professor  of 
mathematics  in  Padua.  At  that  date,  and  in  the 
eightieth  year  of  his  age,  he  published  a  work 
on  natural  philosophy ,  in  which  he  suggested 
taking  the  melting-point  of  ice  and  the  boil- 
ing-point of  water  for  two  fixed  points  of  ther- 
mometer scales,  and  dividing  the  space  between 
them  into  twelve  equal  parts.  This  truly  ad- 
mirable proposition  was  not  appreciated  by  his 
contemporaries  who  did  not  wholly  believe  in 
the  constancy  of  these  temperatures,  and  it  was 


SCALES  FROM  BOYLE  TO  NEWTON.      57 

forgotten  by  succeeding  philosophers,  thus  de- 
laying greatly  accurate  observations  of  tem- 
perature. 

Dalence  had  anticipated  Renaldini  in  adopt- 
ing the  principle  of  the  subdivision  of  the  in- 
terval between  two  determinable  points,  but 
the  phenomena  chosen  by  the  Frenchman  were 
not  so  reliable  as  those  proposed^by  the  Italian, 
which  were  afterwards  adopted  by  Celsius. 

Renaldini  devised  another  method  for  grad- 
uating thermometers ;  he  plunged  the  ther- 
mometer to  be  graduated  first  in  mashed  ice, 
then  in  a  mixture  of  eleven  parts  cold  water 
plus  one  of  boiling  water,  and  successively  in 
mixtures  of  ten  cold  plus  two  boiling,  nine  cold 
plus  three  boiling,  eight  cold  plus  four  boiling, 
and  lastly  in  boiling  water  itself,  marking  on 
the  scale  the  position  of  the  expanding  fluid  at 
each  immersion.  This  sounds  plausible,  but 
was  shown  by  Wolff  to  be  deceptive  and  un- 
reliable. 

Sir  Isaac  Newton  was  one  of  those  who  at- 
tacked the  thermometrical  problem  of  the  age, 
but  the  scale  proposed  by  this  great  genius  was 
by  no  means  satisfactory ;  he  rejected  alcohol 
as  the  dilating  liquid  and  preferred  "lintseed" 
oil ;  for  fixed  points  in  the  scale  he  chose  the 


58    EVOLUTION  OF  THE  THERMOMETER. 

temperature  of  melting  snow  and  of  the  human 
body,  dividing  the  interval  into  twelve  equal 
parts.  In  his  paper  "Scala  graduum,"  pub- 
lished anonymously  in  the  Philosophical  Trans- 
actions, May,  1701,  Newton  gave  his  method 
of  graduation  ;  he  assumed  that  when  the  in- 
strument was  placed  in  melting  snow  the  lin- 
seed oil  occupied  10,000  parts,  and  found  that 
the  same  oil  at  the  temperature  of  the  human 
body,  which  he  called  one  degree  of  heat,  oc- 
cupied a  space  of  10,256  parts;  in  water  boil- 
ing violently  10,725  parts,  and  in  melted  tin 
beginning  to  cool  11,51 6  parts;  from  this  he 
computed  the  degrees  of  heat  corresponding  to 
the  phenomena,  calling  the  heat  of  the  human 
body  12,  he  found  for  boiling  water  34,  and 
melting  tin  72.-  His  thermometer  was  three 
feet  long  and  had  a  bulb  two  inches  in  diameter. 
Newton  also  made  an  experiment  with  a 
thick  piece  of  iron  as  a  pyrometer ;  he  heated 
it  red  hot  and  uput  it  in  a  cold  place  where 
the  wind  blew  uniformly,"  then  he  placed  on 
the  bar  particles  of  various  metals  and  other 
fusible  bodies  and  noted  the  times  of  cooling, 
until  all  the  particles  having  lost  their  fluidity 
grew  cold,  and  the  heat  of  the  iron  was  equal 
to  that  of  the'  human  body.  Then  by  assu- 


SCALES  FROM  BOYLE  TO  NEWTON.      59 

ming  that  the  excesses  of  the  heats  of  the  iron 
and  of  the  solidified  substances,  above  the  heat 
of  the  atmosphere,  were  in  geometrical  pro- 
gression when  the  times  were  in  arithmetical 
progression,  all  the  heats  were  obtained.  From 
this  experiment  and  computation  Newton  drew 
up  the  following  scale  of  degrees  of  heat. 
NEWTON'S  TABLE. 

Degrees    Equal 

of         parts  of  Phenomena, 

heat.        heat. 

f  heat  of  the  winter  air  when  water 

\     begins  to  freeze. 

/  greatest  heat  of  the  surface  of  the 

I      human  body. 

2  24  heat  of  melting  wax. 

2.5        34  heat  of  water  boiling  vehemently, 

g          f  lowest  heat  at  which  equal  parts  of 

I      tin  and  bismuth  melt. 
4          96  lowest  heat  at  which  lead  melts. 

f  heat  of  a  small  coal  fire  not  urged 

\     by  bellows. 

Biot,  commenting  on  Newton's  paper,  notes 
that  it  contains  three  important  discoveries : 
(i)  a  method  of  making  thermometers  compar- 
able by  determining  the  extreme  terms  of  their 
graduation  from  the  phenomena  of  constant 
temperature  ;  (2)  the  determination  of  the  law 
of  cooling  in  solid  bodies  at  moderate  temper- 
atures ;  (3)  observation  of  the  constancy  of  tem- 
perature in  fusion  and  ebullition. 


60    EVOLUTION  OF  THE  THERMOMETER. 

From  Newton's  note-books  it  appears  that 
he  was  occupied  with  these  studies  in  March, 
1692-3,  although  they  were  not  made  public 
until  1701. 

Newton  made  no  use  of  the  boiling-point  of 
water  in  constructing  his  scale  of  temperatures, 
as  he  considered  it  variable ;  he  recorded  that 
water  begins  to  boil  at  33°  of  his  scale,  and 
boils  vehemently  at  34°  to  34^°.  We  now 
know  that  such  fluctuations  depend  upon  the 
position  of  the  thermometer  (which  must  not 
be  immersed  in  the  liquid),  on  the  pressure  of 
the  atmosphere,  on  the  chemical  purity  of  the 
water,  and  on  the  shape  of  the  vessel  holding 
it,  so  it  is  not  surprising  that  doubts  existed 
as  to  the  constancy  of  the  phenomenon.  Mari- 
otte  had  laid  the  foundations  of  hypsometry, 
but  the  experimental  proofs  were  not  secured 
until  L,e  Monnier  tested  the  matter  in  the 
Pyrenees  in  1739. 

In  the  same  year  that  Newton  published  his 
researches,  Etienne  Francois  Geoffrey  de- 
scribed an  open  air-thermoscope  nearly  identi- 
cal with  that  of  Athanasius  Kircher,  made  in 
the  year  1643,  an<^  to  which  the  French  savant 
made  no  allusion.  (Phil.  Trans.,  1701,  p.  951.) 


FAHRENHEIT  THERMOMETERS.          61 

IV.  FAHRENHEIT  AND  THE  FIRST  RELIABLE 
THERMOMETERS. 

The  eminent  French  physicist,  Guillaume 
Amontons,  lost  his  hearing  when  a  schoolboy, 
and  like  the  philosopher  of  old  who  destroyed 
his  eyesight  for  fear  visual  impressions  should 
disturb  his  speculations,  the  Frenchman  de- 
clined surgical  and  medical  assistance  lest  the 
admission  of  common  noises  to  his  brain  should 
interfere  with  his  profound  studies  in  mathe- 
matics and  mechanics.  He  became  skilled  in 
surveying,  able  in  architecture  and  distin- 
guished in  pure  mathematics,  and  he  made 
important  improvements  in  the  hygrometer, 
the  barometer,  and  the  thermometer. 

Amontons  constructed  the  first  veritable  air- 
thermometer  which  was  not  at  the  same  time 
a  barometer ;  it  consisted  of  a  narrow  glass 
tube  four  feet  long,  open  above,  ending  below 
in  a  large  bulb  connected  by  a  U-shaped  bend  ; 
in  this  bulb  air  was  confined  by  a  column  of 
mercury  so  adjusted  that  when  the  apparatus 
was  immersed  in  boiling  water,  the  barometer 
standing  at  28  inches,  the  mercury  in  the  tube 
stood  45  inches  above  the  level  in  the  bulb, 
thus  making  the  pressure  of  the  heated  air  73 
inch'es.  The  tube  was  graduated  from  73 


62     EVOLUTION  OF  THE  THERMOMETER. 

inches  down  in  inches  and  lines  (pouces  and 
lignes),  so  that  on  this  scale  51.5  inches  were 
equal  to  o°  C.,  and  73  inches  to  100°  C.  Read- 
ings were  corrected  by  a  barometer.  This  in- 
strument registered  the  changes  in  the  elastic 
force  of  air  produced  by  heat,  and  was  styled 
by  Amontons  the  "universal  thermometer;" 
but  its  great  length,  the  difficulty  of  transport- 
ing it,  and  the  inaccuracy  due  to  friction  of 
mercury  in  the  glass  tube,  prevented  it  from 
being  adopted. 

Amontons  is  often  credited,  especially  by 
French  authors,  with  the  discovery  that  the 
boiling-point  of  water  is  constant  under  like 
conditions  as  respects  pressure,  etc.,  but  this 
cannot  be  sustained  for  it  is  certain  that  Ren- 
aldini  anticipated  him  in  proposing  the  boil- 
ing-point of  water  as  a  fixed  point,  and  that 
Boyle  and  Papin  demonstrated  the  influence  of 
pressure  long  before. 

The  French  physicist  constructed  a  mercury 
thermometer  provided  with  a  double  scale  as- 
cending from  49  to  59  and  descending  from  14 
to  24 ;  in  this  were  the  following  correspon- 
dences :  59°  =  solidification  of  tallow ;  54°  = 
cellars  of  the  observatory,  Paris;  52°  —  freez- 
ing of  water.  This  instrument  had  no  advan- 
tages over  those  in  use. 


FAHRENHEIT  THERMOMETERS.         63 

Commenting  on  the  experiments  of  Sir  Isaac 
Newton  with  the  iron  pyrometer,  Amontons 
devised  similar  ones.  Assuming  that  the  tem- 
perature increased  in  arithmetical  progression 
throughout  a  rod  of  iron  59  inches  long,  he 
obtained  the  following  results. 

TEMPERATURES  OBTAINED  WITH  AMONTON'S 

PYROMETER. 

Thin  glass  melted  at          4  pouces  4  lignes. 
Lead  melted  at  8  pouces  6  lignes. 

Gunpowder  ignited  at        8  pouces  6  lignes. 
Tin  melted  at  n  pouces 

Alloy  of  3  tin  and  2  ) 

lead  melted  at  j    I2  Pouces 

Water  boiled  at  22  pouces 

White  wax  melted  at       30  pouces  8  lignes. 
Tallow  melted  at  39  pouces 

Butter  melted  at  42  pouces 

In  his  paper  published  in  the  "  Memoirs  de 
Paris  "  (i  703,  p.  50)  Amontons  makes  the  oracu- 
lar statement  "heat  is  the  soul  of  nature,  and 
it  is  very  important  for  physicists  to  be  able  to 
measure  it  accurately." 

Fourteen  years  later,  Jakob  Hermann,  a 
mathematical  physicist  of  Basle,  seeking  to 
make  thermometrical  readings  independent  of 
corrections  for  barometric  pressure,  proposed 
to  close  the  tubes  of  Amontons'  air  thermom- 
eters *  by  fusing  the  upper  ends ;  this  form  of 


64    EVOLUTION  OF  THE  THERMOMETER. 

instrument  he  described  in  a  work  entitled : 
"  Phoronomia,"  published  at  Amsterdam  in 
1716.  This  instrument  showed  directly  the 
elasticity  of  the  confined  air,  and  thereby  the 
temperature,  a  correction  being  made  for  the 
temperature  of  the  column  of  mercury. 

Frequent  allusions  to  the  thermometer  of 
Philippe  de  la  Hire  are  met  with  in  works  on 
meteorology,  and  his  instrument  was  famous 
not  because  of  its  novel  construction,  but  owing 
to  the  long  series  of  observations  conducted 
with  it  and  published  in  the  Memoirs  'of  the 
Academy  of  Sciences,  beginning  with  the  year 
1670.  It  was  a  Florentine  thermometer  having 
a  scale  the  value  of  which  has  never  been  ac- 
curately determined;  La  Hire  considered  it 
sufficient  to  state  that  it  had  two  fixed  points, 
the  temperature  of  a  deep  cellar  in  the  ob- 
servatory (48°)  and  that  of  the  air  in  an  open 
room  when  it  was  freezing  in  the  vicinity. 

Amontons  sought  to  compare  his  standard 
thermometer  with  that  of  La  Hire,  but  could 
not  obtain  permission  from  the  authorities  to 
place  his  instrument  alongside  of  it  in  the  ob- 
servatory; after  his  death  a  superficial  com- 
parison was  made.  Lambert  says  the  zero  of 
La  Hire's  scale  was  the  temperature  of  a  mix- 


FAHRENHEIT  THERMOMETERS.         65 

ture  of  snow  and  salt,  and  the  100  degrees  was 
the  temperature  of  melted  tallow  about  to 
solidify. 

It  is,  of  course,  inexpedient  to  attempt  to 
chronicle  in  this  volume  every  printed  note 
on  the  thermometer,  many  of  which  did  not 
bring  their  authors  much  fame,  and  did  little 
to  advance  the  instrument  to  perfection.  But 
brief  reference  may  be  made  to  a  "  Disserta- 
tion" by  Gabriel  Philippe  de  la  Hire,  (Memoires 
Acad.  Science,  Paris,  1706,  p.  432),  (son  of 
Philippe  just  named)  in  which  he  mentions  an 
instrument  invented  by  Nugent  in  1706,  re- 
sembling that  of  Huyghens,  and  to  a  short  ar- 
ticle on  the  "Construction  of  Thermometers," 
by  Elias  Cammerarius  in  1712  (Ephem.  Acad. 
Nat.  Curiosa,  C.  i  and  2,  p.  370),  before  we 
consider  the  eminent  services  to  thermometry 
rendered  by  Fahrenheit. 

In  the  year  1714,  Christian  Freiherr  von 
Wolf,  Chancellor  of  the  University  of  Halle, 
and  professor  of  mathematics  and  philosophy 
in  the  same,  received  a  visit  from  Fahrenheit, 
a  maker  of  philosophical  apparatus  in  Amster- 
dam, who  presented  him  with  two  thermom- 
eters made  by  himself,  which  agreed  so  per- 
fectly in  registering  temperatures  that  the 


66   'EVOLUTION  OF  THE  THERMOMETER. 

learned  professor  was  amazed  ;  he  considered 
the  unusual  phenomenon  so  remarkable  that 
he  wrote  a  paper  for  the  Acta  Eruditorum  in 
the  same  year,  ascribing  the  concordance  to 
certain  singular  properties  of  the  alcohol.  Noth- 
ing can  illustrate  more  cogently  the  imperfec- 
tions of  the  best  instruments  then  in  scientific 
hands,  and  the  character  of  those  in  ordinary 
use  can  be  imagined ;  nothing  can  better  demon- 
strate the  immense  advance  made  by  Fahren- 
heit, and  even  those  who  deprecate  the  wide 
use  of  his  illogical  scale  must  pay  tribute  to 
the  value  of  his  services  in  developing  reliable 
thermometers. 

Daniel  Gabriel  Fahrenheit  was  born  at  Dan- 
zig, 24th  May,  1686,  the  son  of  a  well-to-do 
merchant.  After  receiving  private  instruction 
at  home  he  attended  the  gymnasium,  but  when 
fifteen  years  old  he  had  the  misfortune  to  lose 
both  his  parents  in  one  day(i4  Aug.,  1701), 
and  wras  then  sent  to  Amsterdam  to  enter  a 
business  house.  There  he  completed  his  ap- 
prenticeship of  four  years,  but  forsook  com- 
merce in  order  to  follow  his  inclination  to  study 
physical  science  and  to  travel ;  he  became  in- 
terested in  meteorology  and  acquired  great 
skill  in  constructing  thermometers.  In  1714 


FAHRENHEI7   THERMOMETERS.         67 


he  visited  glass-works  in  Berlin  and  Dresden 
to  supervise  the  manufacture  of  the  tubes  for 
his  instruments,  and  on  this  journey  he  called 
on  Professor  von  Wolf  in  Halle,  as  stated. 

Returning  to  Amsterdam  he  established  him- 
self as  a  maker  of  philosophical  instruments  ; 
at  that  period  three  distinguished  men  of  science 
honored  Holland,  Dr.  Hermann  Boerhaave,  pro- 
fessor of  medicine  and  chemistry  in  Leyden, 
Pieter  van  Musschenbroek,  professor  of  mathe- 
matics and  physics  in  Utrecht,  and  Willem 
Jacob  van  'sGravesande,  astronomer  and  math- 
ematician at  the  Hague,  and  these  refer  in  their 
writings  to  Fahrenheit  and  his  thermometers. 
When  he  visited  England  some  time  prior  to 
1724,  he  was  well  received  and  honored  by 
election  to  membership  in  the  Royal  Society. 
Fahrenheit  died  unmarried  in  the  land  of  his 
adoption  i6th  September,  1736,  at  the  age  of 
fifty  years  ;  he  was  buried  in  the  Klosterkirche 
in  the  Hague. 

Fahrenheit's  practical  work  in  thermometry 
began  as  early  as  1  706  ;  at  first  he  used  alcohol 
only,  but  afterwards  became  famous  for  his 
mercury  thermometers.  In  1709  he  sent  his 
instruments  to  distant  places,  Iceland  and  Lap- 
land", and  took  them  in  person  to  Sweden  and 

/ 


68    EVOLUTION  OF  THE  THERMOMETER. 

Denmark.  For  eighteen  years  Fahrenheit  kept 
secret  his  method  of  manufacture  for  commer- 
cial reasons,  but  between  1724  and  1726  he 
published  five  brief  papers  in  the  Philosoph- 
ical Transactions.  Many  of  the  experiments 
date,  however,  from  1721. 

In  the  first  of  these  he  gives  the  specific  grav- 
ity and  boiling-points  of  five  liquids,  alcohol, 
rain-water,  nitric  acid,  potash-lye,  and  sulfuric 
acid,  taken  at  48°  of  his  scale ;  this  tempera- 
ture, he  explains,  is  half-way  between  that  of 
the  intense  cold  obtained  by  a  mixture  of  water, 
ice  and  sal-ammoniac,  or  common  salt,  and 
that  of  the  blood  of  man. 

The  second  paper,  on  the  freezing  of  water 
in  vacuo,  contains  the  interesting  observation 
that  water  can  remain  liquid  below  its  freez- 
ing-point; incidentally  Fahrenheit  describes 
his  thermometer. 

The  third  paper  contains  the  specific  gravity 
of  29  substances,  solid  and  liquid,  the  deter- 
mination having  been  made  with  the  balance 
and  with  the  new  hydrometer  described  in 
paper  No.  4.  This  instrument  was  the  first 
hydrometer  of  constant  volume ;  it  had  a  pan 
for  carrying  weights  like  Nicholson's  (which 


FAHRENHEIT  THERMOMETERS.        69 

was  patterned  after  it),  and  was   the  first  that 
could  be  used  for  all  liquids. 

In  the  fifth  paper  Fahrenheit  describes  his 
invention  of  the  thermo-barometer,  based  on 
the  fact  that  the  boiling-boint  of  water  is  in- 
fluenced by  barometric  pressure.  Boyle  had 
observed  the  lowering  of  the  boiling-point  un- 
der the  receiver  of  the  air-pump,  but  Fahren- 
heit was  the  first  to  discover  the  principles  of 
hypsometry. 

Fahrenheit's  publications  are  few  in  number 
and  very  brief,  but  they  show  him  to  have  been 
an  original  thinker,  and  his  great  mechanical 
skill  in  working  glass  enabled  him  to  carry  out 
his  designs.  His  account  of  the  thermometer 
is  of  so  great  interest  that  I  give  it  entire. 

"The  thermometers  constructed  by  me  are 
chiefly  of  two  kinds,  one  is  filled  with  alcohol 
and  the  other  with  mercury.  Their  length 
varies  with  the  use  to  which  they  are  put,  but 
all  the  instruments  have  this  in  common :  the 
degrees  of  their  scales  agree  with  one  another 
and  their  variations  are  between  fixed  limits. 
The  scales  of  thermometers  used  for  meteoro- 
logical observations  begin  below  with  o°  and 
go  to -96°.  The  division  of  the  scale  depends 
upon  three  fixed  points  which  are  obtained  in 
5 


70    EVOLUTION  OF  THE  THERMOMETER. 

the  following  manner :  The  first  point  below, 
at  the  beginning  of  the  scale,  was  found  by  a 
mixture  of  ice,  water  and  sal-ammoniac,  or  also 
sea-salt ;  when  a  thermometer  is  put  in  such  a 
mixture  the  liquid  falls  until  it  reaches  a  point 
designated  as  zero.  This  experiment  succeeds 
better  in  winter  than  in  summer.  The  second 
point  is  obtained  when  water  and  ice  are  mixed 
without  the  salts  named ;  when  a  thermometer 
is  put  into  this  mixture  the  liquid  stands  at  32°, 
and  this  I  call  the  commencement  of  freezing, 
for  still  water  becomes  coated  with  a  film  of 
ice  in  winter  when  the  liquid  in  the  thermom- 
eter reaches  that  point.  The  third  point  is  at 
96°  ;  the  alcohol  expands  to  this  height  when 
the  thermometer  is  placed  in  the  mouth,  or  the 
arm-pit,  of  a  healthy  man  and  held  there  until 
it  acquires  the  temperature  of  the  body.  If, 
however,  the  temperature  of  a  person  suffering 
from  fever,  or  some  other  disease,  is  to  be  taken 
another  thermometer  must  be  used  having  a 
scale  lengthened  to  128°  or  132°.  Whether 
these  degrees  are  high  enough  for  the  hottest 
fevers  I  have  not  examined ;  I  do  not  think, 
however,  that  the  degrees  named  will  ever  be 
exceeded  in  any  fever. 

"The  scales  of  such  thermometers  as  are 


FAHRENHEIT  THERMOMETERS,         71 

used  for  determining  the  boiling-points  of 
liquids  begin  also  at  o°  and  run  up  to  600°, 
for  at  about  this  temperature  mercury  begins 
to  boil.  To  increase  the  sensitiveness  of  ther- 
mometers they  are  made  with  cylinders  instead 
of  spheres,  so  that  a  larger  surface  will  be  more 
quickly  affected." 

Fahrenheit  then  gives  a  full  account  of  his 
method  of  filling  thermometers  with  liquids,  a 
practical  feature  not  necessary  to  detail  in  this 
place.  The  fever  thermometers  were  known 
as  "Pyranthropometers." 

While  these  scanty  records  are  all  given  us 
by  Fahrenheit  himself,  other  details  are  fur- 
nished by  contemporary  writers  ;  Christian  von 
Wolf  describes  the  instruments  given  him  by 
Fahrenheit  thus : 

The  two  thermometers  had  cylinders  in 
place  of  spheres  and  were  filled  with  colored 
alcohol.  The  cylinder  of  one  was  one  and 
three-eighths  inches  long  (12  inches  to  a  Paris 
foot),  thirteen  sixty-fourths  inch  in  diameter, 
and  the  lower  portion  ended  in  a  sphere  ;  the 
tube  was  six  and  eleven-sixteenths  inches  long. 
The  scale  was  six  and  seven-sixteenths  inches 
long  f. nd  had  26  degrees,  each  of  which  was 
divided  into  four.  The  second  degree  on  the 


72    EVOLUTION  OF  THE  THERMOMETER. 

cylinder  was  marked  "greatest  cold"  (o°  F.), 
and  from  this  to  the  upper  end  were  24  de- 
grees, some  bearing  special  names;  the  fourth 
was  uvery  cold,"  the  eighth  "cold,"  the  twelfth 
"moderate,"  the  sixteenth  "warm,"  the  twen- 
tieth "  very  hot,"  and  the  twenty-fourth  "  un- 
bearable heat."  The  second  tube  of  Wolf  dif- 
fered little  in  size.  Wolf  tested  the  two  instru- 
ments and  found  the  slight  difference  between 
them  of  one-four  hundred  and  sixteenth  of  the 
entire  scale. 

Another  friendly  contemporary  of  Fahren- 
heit, Dr.  Hermann  Boerhaave,  has  recorded  in 
his  "  Elements  of  Chemistry"  some  particulars 
of  the  celebrated  thermometers*.  Boerhaave, 
writing  in  1731,  ascribes  the  invention  of  the 
thermometer  to  Drebbel,  cites  Amontons,  Mari- 
otte,  and  others,  and  gives  an  account  of  a  note- 
worthy experiment  made  by  Fahrenheit,  who 
poured  spirit  of  nitre  on  ice  and  got  a  temper- 
ature of  — 29°  F.,  using  an  instrument  gradu- 
ated to  —79°.  Boerhaave  then  describes  "an 
elegant  thermometer  made  at  his  request  by 
the  skilled  artist  Daniel  Gabriel  Fahrenheit " 
thus:  " The  lower  cylinder  of  this  instrument 
contains  11,124  parts  of  mercury,  which  in  the 
utmost  cold  observed  in  Iceland  reached  to  the 


FAHRENHEI7   THERMOMETERS.         73 

mark  o  from  whence  the  further  degrees  of 
heat  are  computed  upwards.  Now  if  this  be 
immersed  in  a  vessel  of  water  gradually  heated, 
the  mercury  will  be  found  to  ascend  continu- 
ally till  the  water  comes  to  boil,  at  212°  or 
more ;  so  that  setting  aside  the  dilatation  of  the 
glass  it  now  possesses  11,336  spaces  of  which 
in  the  greatest  cold  it  possessed  11,124,  so  that 
by  this  difference  of  heat  the  bulk  is  dilated  to 

i 
"52"-  25  / 

53 

In  another  passage,  Boerhaave  relates  that 
on  comparing  two  of  Fahrenheit's  thermom- 
eters, one  of  alcohol  and  one  of  mercury,  he 
found  a  slight  discrepancy  and  reported  it  to 
the  maker,  who  "ingeniously  owned  the  fail- 
ing, but  did  not  then  see  the  cause  of  it,  but 
revolving  it  in  his  own  mind  he  at  length  dis- 
covered that  the.  very  glass  made  in  Bohemia, 
England,  and  Holland  expands  more  or  less 
easily  by  the  same  degree  of  heat,"  and  Fahren- 
heit suggested  that  the  two  instruments  ought 
to  be  made  of  one  kind  of  glass.  Thereupon  the 
doctor  adds  this  comment :  "How  circumspect 
does  nature  require  us  to  be  in  order  to  dis- 
cover truth  in  physical  matters,  and  how  often 
are  we  deceived  by  following  a  general  rule." 


74    EVOLUTION  OF  THE  THERMOMETER. 

Fahrenheit  made  his  thermometers  with  dif- 
ferent scales  at  different  times,  commonly  known 
as  the  large,  medium,  and  small  scales,  their 
correspondence  and  value  being  shown  in  the 
table. 

i.  ii.  in. 

I,arge.  Medium.  Small.  (Centigrade.) 

90  24  96  35.5 

o  12  48  8.8 

— 90  o  o  — 17.8 

In  No.  I  the  o°  was  placed  at  "temperate" 
as  in  the  Florentine  scale ;  in  No.  II  each  space 
was  divided  into  four  equal  parts,  and  these 
smaller  divisions  were  afterwards  taken  as  de- 
grees, thus  forming  scale  No.  III. 

The  earliest  thermometers  were  made  to  in- 
dicate temperature  up  to  96°  only ;  it  does  not 
appear  that  Fahrenheit  used  the  boiling-point 
of  water  as  a  fixed  point,  although  he  alludes 
in  his  first  paper  to  the  fact  that  Amontons 
had  shown  that  water  boils  at  a  constant  tem- 
perature. The  origin  of  the  numbers  32  for 
the  freezing-point  and  212  for  the  boiling-point 
of  water  is  obscure,  they  may  have  arisen  in 
this  way:  After  Fahrenheit  abandoned  the 
Florentine  scale  — 90-0-90,  he  arbitrarily 
contrived  the  scale  o- 12-24  taken  from  the 
familiar  foot  measure,  but  the  spaces  being  too 


FAHRENHEIT  THERMOMETERS.         75 

large  for  accurate  readings  each  was  divided 
into  four,  and  thus  arose  the  scale  0-48-96. 
When  he  made  thermometers  for  higher  tem- 
peratures the  scale  was  merely  lengthened  by 
adding  more  spaces  of  equal  size,  and  one  of 
the  divisions  marked  212  accidentally  coincided 
with  the  level  of  the  liquid  at  the  boiling-point 
of  water  ;  Fahrenheit  never  had  any  intention 
of  dividing  the  interval  between  his  zero  and 
the  boiling-point  of  water  into  212  parts. 

It  is  a  singular  thing,  however,  that  if  we 
adopt  the  fixed  points  32  and  212,  the  actual 
temperature  of  the  human  body  is  98°  not  96°  ; 
so  the  Fahrenheit  scale  now  in  use  is  not  ex- 
actly the  original.  Moreover  the  zero  of  the 
Florentine  thermometer  is  given  by  him  as 
equal  to  45°  F.  and  by  others  as  48°. 

Uncertainty  also  exists  as  to  the  exact  tem- 
perature selected  by  Fahrenheit  for  his  zero; 
the  proportions  of  ice,  water,  and  salt  (or  sal- 
ammoniac)  in  the  mixture  he  used  are  un- 
known. RiidorfT  has  shown  that  the  temper- 
ature obtained  by  mixing  100  parts  of  snow 
and  33  of  salt  equals  —21.3°  C.,  and  100  parts 
snow  with  25  of  sal-ammoniac  gives  — 15.4° 
C.,  whereas  the  modern  Fahrenheit  zero  is  equal 
to  -^7.8°  C.  Fahrenheit's  original  mixture 


76    EVOLUTION  OF  THE  THERMOMETER. 

must  have  contained  the  two  salts  in  propor- 
tions now  indeterminable. 

According  to  Boerhaave,  Fahrenheit's  zero 
coincides  with  the  greatest  natural  cold  ob- 
served in  Iceland  in  the  winter  of  1 709,  and 
this  is  sometimes  stated  to  have  been  the  origin 
of  the  lower  fixed  point  in  the  scale.  Surely 
that  winter  was  remarkably  mild  in  frozen 
Iceland,  for  zero  is  often  exceeded  in  countries 
not  regarded  as  arctic  ;  yet  Boerhaave  remarks 
that  "  nature  never  produced  a  cold  beyond 
zero."  The  Meteorological  Yearbook  for  Den- 
mark shows  that  the  temperature  fell  in  March 
1888,  at  Stykkisholm,  Iceland,  to  —8.5°  F. 

There  is  another  element  of  uncertainty  in 
Fahrenheit's  scale.  Both  Musschenbroek  and 
Boerhaave  state  that  the  bulb  of  Fahrenheit's 
thermometer  contains  11,124  parts  of  mercury 
at  zero  and  that  when  the  bulb  is  placed  in 
melting  ice  the  metal  expands  32  of  these 
parts;  but  Boerhaave,  in  another  place,  says 
the  bulb  contains  10,872  parts  of  mercury, 
and  in  still  a 'third  passage  he  gives  the  num- 
ber of  parts  as  11,520,  which  Dr.  Martine  ap- 
prehends is  nearer  the  truth.  These  vaguely 
named  "parts"  depend  upon  the  figures~taken 
for  the  expansion  of  mercury;  to  show  their 


FAHRENHEIT  THERMOMETERS.          77 

derivation  we  must  bear  in  mind  that  the  ratio 
between  the  capacity  of  the  bulb  and  of  the 
stem  is  constant  for  equal  increments  of  heat. 

Let  x  =  the  quantity  of  mercury  in  the  bulb 

at  32°, 

1 80  =  number  of  degrees  between  the  boiling- 
point  and  freezing-point  of  water, 

161.7 

—  =  expansion   of  mercury  between  these 

10,000 

two  temperatures, 
then:    161.7  :  10,000  =  180  :  x,  and  x  =  11,124. 

(Fahrenheit's  figure  161.7  is,  however,  erron- 
eous, it  should  be  181.53.) 

A  number  of  Fahrenheit's,original  thermom- 
eters are  preserved  in  European  institutions ; 
two  are  in  the  physical  cabinet,  Leyden,  one 
653  mm.  long  is  graduated  from  — 4°  to  600°, 
the  other  one  is  232  mm.  long  and  has  a  scale 
from  —4°  to  100°.  Both  are  filled  with  mer- 
cury. Comparison  with  a  modern  standard 
thermometer  shows  that  the  freezing-point  of 
water  in  the  larger  one  is  34.2°,  and  in  the 
smaller  34.1°.  The  Real  Gymnasium  of  St. 
Peter,  in  Danzig,  treasures  one  of  Fahrenheit's 
early  thermometers;  it  is  filled  with  alcohol, 
measures  no  mm.  in  length,  and  has  attached 
in  P  glass  tube  a  paper  scale  graduated  from 


78    EVOLUTION  OF  THE  THERMOMETER. 

o°  to  100°.  Above  the  scale  is  the  inscription  : 
"  Cilinder  termometron  Ferneid." 

Fahrenheit  was  followed  almost  immediately 
by  a  host  of  imitators,  each  devising  a  scale 
differing  from  Fahrenheit's  and  from  one  an- 
other, none  of  them  possessing  any  special  ad- 
vantage. In  1712  to  1713,  Fahrenheit,  being 
in  Berlin,  communicated  his  method  of  con- 
structing thermometers  to  his  teacher  of  higher 
mathematics,  Prof.  Barnsdorf,  and  the  latter 
made  instruments  with  a  scale  of  his  own,  the 
relation  being  as  follows : 

Fahrenheit.  Barnsdorf. 

96  13 

18  ii 

4-5  o 

O  —I 

Barnsdorf  taught  the  art  to  Dr.  Lange,  pro- 
fessor of  mathematics  in  Halle,  and  he  devised 
a  scale  of  his  own : 

Fahrenheit.  I^ange. 
96  24 

52.3  12 

48  10.8 

6.4  o 

O  -1.7 

Besides  these  imitators  of  Fahrenheit  there 
may  be  named  Christian  Kirch,  professor  of 
astronomy  in  Berlin,  Chr.  Friedr.  Ludolff, 


REAUMUR  AND  CELSIUS.  79 

Sisson,  and  Bergen,  whose  scale  made  32° 
Fahrenheit  =  6°  B.,  and  212°  Fahrenheit  — 
174°  B.  Michael  Christian  Hanow,  of  Dan- 
zig, adopted  a  scale  in  which  two  degrees  Fah- 
renheit equaled  one  degree  H.;  having  ob- 
served in  1740  that  the  alcohol  in  a  Fahren- 
heit thermometer  fell  to  ten  degrees  below  zero, 
he  immediately  devised  a  scale  in  which  the 
zero-point  was  lowered  ten  degrees. 

These  objectionable  imitations  of  Fahren- 
heit's thermometers  brought  the  genuine  ones 
into  evil  repute,  but  the  latter  outlived  their 
rivals  and  Fahrenheit's  scale  is  the  popular  one 
wherever  English  is  spoken.  The  weakness 
of  Fahrenheit's  scale  was  the  three  fixed  points 
somewhat  vaguely  defined. 

V.     THERMOMETERS  OF  REAUMUR,  CELSIUS, 

AND  OTHERS. 

Thermometers  for  a  special  and  limited  use 
were  manufactiired  about  1727  by  John  Fow- 
ler, Swithin's  alley,  near  the  Royal  Exchange, 
London ;  these  were  adapted  to  the  cultivation 
of  hot-house  plants,  being  graduated  to  indi- 
cate degrees  most  "kindly"  to  given  plants. 
The  instruments  varied  in  length  from  18 
inches  to  4  feet,  and  the  stems  were  marked 


8o    EVOLUTION  OF  THE  THERMOMETER. 

from  freezing-point  of  water  to  90°  a  tempera- 
ture equal  to  that  of  warm  water  capable  of 
being  endured  by  the  hand  held  still,  certainly 
a  very  vague  standard  but  perhaps  sufficiently 
accurate  for  vegetable  life. 

The  proper  temperatures  for  specified  plants 
were  as  follows,  the  degrees  being  those  given 
by  Hales. 

HALES'  TABLE. 

Melon  thistles       .  .  .  31 

Ananas  .  .  .  .29 

Piamento  ...  26 

Euphorbium  .  .  .  .24 

Cereus       .  .  .  .  21 

Aloes  ....          19 

Indian  figs  .  .  .  16 

Ficoides  .  .  .   •         .          14 

Oranges  .  .  .  12 

Mistles  ....  9 

(Phil.  Trans.,  Apr. -June,  1727.) 
These  instruments  were  used  by  the  eminent 
botanist,  Rev.  Stephen  Hales,  who  describes 
them  in  his  "Vegetable  Statics,"  1727  (p.  61). 
Dr.  Hales  remarks  that  "64  of  these  degrees 
is  nearly  equal  to  the  heat  of  the  blood  of  ani- 
mals," which  he  determined  by  placing  the 
"ball  of  the  thermometer  in  the  blood  of  an 
expiring  ox."  The  "temperate"  point  was 
about  1 8  of  these  degrees. 


REAUMUR  AND  CELSIUS.  Si 

Reaumur,  who  next  sought  to  improve  the 
thermometer,  was  one  of  the  most  popular  sa- 
vants in  France ;  his  position  in  the  world  of 
science  as  well  as  in  that  of  society,  was  far 
more  conspicuous  than  that  of  the  humble  ar- 
tisan Fahrenheit,  and  his  aristocratic  station 
is  evidenced  by  his  full  name :  Rend  Antoine 
Ferchault,  Seigneur  de  Reaumur,  des  Angles 
et  de  la  Bermondiere.  He  early  became  a 
member  of  the  French  Academy  of  Sciences, 
and  for  more  than  fifty  years  assiduously  cul- 
tivated the  sciences ;  his  studies  embraced  the 
industrial  arts,  the  physical  and  the  natural 
sciences,  and  his  publications  were  very  nu- 
merous. In  the  Memoirs  of  the  Academy  of 
Sciences  for  1731  he  published  a  long  paper 
entitled :  "  Rules  for  the  Construction  of  Ther- 
mometers with  Comparable  Scales,"  which  in 
its  verbosity  and  prolixity  contrasts  strongly 
with  Fahrenheit's  conciseness. 

Reaumur,  like  so  many  Frenchmen,  com- 
pletely ignored  the  thermometrical  labors  of 
the  German,  and  rejected  quicksilver,  owing  to 
its  small  coefficient  of  expansion ;  he  sought 
by  means  of  dilute  alcohol  to  arrange  a  scale 
sa  that  a  definite  change  in  volume  would  cor- 
respond to  a  definite  rise  or  fall  in  temperature. 


82    EVOLUTION  OF  THE  THERMOMETER. 

He  adopted  a  single  fixed  point,  the  freezing- 
point  of  water,  a  constant  more  difficult  to  de- 
termine accurately  than  the  melting-point  of 
ice ;  he  ascertained  that  alcohol  diluted  with 
one-fifth  water  expanded  from  1000  to  1080 
volumes  between  the  freezing-  and  boiling- 
points  of  water,  and  so  he  took  zero  for  the 
lower  and  80  for  the  higher  temperature,  divi- 
ding the  intervening  space  into  80  parts. 

Reaumur  showed  much  ingenuity  in  his  ex- 
perimental work,  but  in  his  theoretical  conclu- 
sions he  made  serious  errors ;  he  believed  er- 
roneously that  he  obtained  the  temperature  of 
boiling  water  by  immersing  the  unsealed  alco- 
hol tube  in  boiling  water,  and  he  ignored  the 
influence  of  air-pressure,  although  Fahrenheit's 
experiments  were  generally  known.  For  these 
and  other  reasons  his  thermometers  were  not 
satisfactory ;  with  bulbs  three  to  four  inches 
in  diameter  the  instruments  were  too  large  for 
standardizing  smaller  ones,  and  attempts  to 
transfer  Reaumur's  scale  to  mercury  thermom- 
eters led  to  confusion.  Lambert,  writing  in 
1779,  gives  for  Reaumur  three  scales:  first, 
that  intended  by  him,  second,  the  so-called 
Reaumur  scale  applied  to  mercury  thermom- 
eters, and  third,  the  scale  actually  obtained  by 


REAUMUR  AND  CELSIUS.  83 

the  savant,  which  did  not,  however,  agree  with 
that  proposed  by  him. 

Thermometers  made  after  Reaumur's  plans 
were  constructed  by  the  Abbe  Nollet  (1732), 
by  Tobias  Mayer,  by  Boissier  de  Sauvages,  and 
by  Brisson;  the  latter  proposed  quite  properly 
to  use  the  melting-point  of  ice  rather  than  the 
freezing-point  of  water  as  the  lower  fixed  point, 
and  he  took  the  heat  of  the  human  body  for  a 
second  fixed  point  making  it  equal  to  32^ 
degrees  Brisson. 

The  Abbe  Soumille  constructed  a  thermom- 
eter like  that  of  Reaumur,  but  in  four  sections  ; 
in  the  first  section  the  temperature  of  melting 
ice  was  placed  at  the  top  of  the  tube,  and  the 
tube  was  graduated  downward  to  — 20  at  the 
bottom ;  the  second  section  began  where  the 
first  ended,  the  temperature  of  melting  ice  be- 
ing at  the  bottom  of  the  tube  and  the  scale 
extending  to  -f-  20 ;  the  third  section  ran  from 
20  to  40  and  the  fourth  to  60.  The  spaces  be- 
tween degrees  were  an  inch  long  admitting  of 
fine  subdivision.  (Hist.  Acad.  Sci.,  Paris,  1770, 
p.  112.) 

Reaumur's  methods  were  severely  criticized 
by  De  Luc  in  his  researches  on  the  modifica- 
tions of  the  atmosphere ;  on  the  other  hand 


84    EVOLUTION  OF  THE  THERMOMETER. 

Lambert  makes  the  caustic  remark :  "  Had  De 
Luc  written  a  work  four  times  as  small,  he 
might  have  said  four  times  as  much  as  he  did 
say." 

Shortly  after  Reaumur's  publication  Joseph 
Nicolas  de  1'Isle,  professor  of  astronomy  in  St. 
Petersburg,  devised  a  thermometer  on  the  same 
principles,  but  adopted  as  the  point  of  depar- 
ture the  temperature  of  boiling  water,  calling 
it  zero,  and  adjusting  the  scale  so  that  the 
freezing-point  of  water  equaled  150  degrees. 
This  instrument  was  not  much  used  outside  of 
Russia. 

In  1741,  Jacques  Barthele'nii  Micheli  du 
Crest,  of  Switzerland,  an  army  officer,  presented 
many  arguments  against  the  scale  of  Reaumur ; 
he  used  mercury  only  for  calibrating  tubes  and 
rejected  it  as  a  thermometrical  liquid,  owing  to 
the  great  difficulty  of  purifying  it,  preferring 
alcohol  that  had  stood  the  gunpowder  test.  He 
took  as  one  fixed  point  the  "temperature  of 
the  terrestrial  globe,"  as  observed  in  the  cellar 
of  the  Paris  observatory,  84  feet  deep,  and  as 
the  second  fixed  point  the  boiling-point  of 
water;  the  interval  he  divided  into  100  de- 
grees. The  degrees  in  this  scale  nearly  coin- 
cide with  those  of  Reaumur.  The  thermom- 


REAUMUR  AND  CELSIUS.  85 

eter  of  Du  Crest  was  commonly  used  in  north- 
ern Switzerland,  and  only  a  few  years  ago  aged 
people  often  cited  air-temperatures  in  Du  Crest 
degrees. 

In  1 749  Du  Crest  was  condemned  for  politi- 
cal reasons  to  lifelong  imprisonment,  and  dur- 
ing the  seventeen  years  that  he  spent  in  the 
fortress  at  Aargau  he  published  several  papers 
on  meteorology;  he  died  in  1766. 

Anders  Celsius,  professor  of  astronomy  at 
Upsala,  proposed  in  1742  a  scale  with  zero  at 
the  boiling-point  of  water  (the  barometer  at 
25  inches,  3  lines),  and  with  100  at  the  tem- 
perature of  melting  ice.  Celsius's  scale  is 
sometimes  confounded  with  the  French  cen- 
tesimal scale  now  in  use,  through  neglect  to 
remember  the  inversion.  The  change  to  the 
modern  centigrade  was  made  by  two  scientists 
independently,  Christin,  of  Lyons,  and  Marten 
Stromer,  of  Upsala.  The  Lyons  savant  worked 
out  the  same  plan  as  Celsius  independently  and 
published  his  results  in  the  local  papers  in 
1743.  He  disregarded  the  barometric  pressure 
but  in  other  respects  his  thermometer  did  not 
differ  from  the  mercury  centigrade  thermom- 
eter of  France  ;  Christin's  instrument  was 
knoy.Tn  as  the  thermometer  of  Lyons. 
6 


86    EVOLUTION  OF  THE  THERMOMETER. 

Seven  years  later  Stromer,  a  colleague  of 
Celsius,  also  inverted  the  scale  and  his  ther- 
mometer was  used  in  meteorological  observa- 
tions at  Upsala  from  1750. 

The  centesimal  division  of  the  scale  between 
the  freezing-point  and  the  boiling-point  has 
been  claimed  for  Linnaeus,  the  eminent  Swe- 
dish botanist.  In  1844,  Arago  made  a  commu- 
nication to  the  French  Academy  of  Sciences, 
quoting  a  private  letter  of  Linnaeus,  who  wrote 
that  he  was  the  first  to  construct  a  thermom- 
eter with  the  centesimal  division  of  the  scale 
between  the  freezing-point  and  the  boiling- 
point  of  water,  for  use  in  a  green-house.  Un- 
fortunately the  date  of  Linnaeus'  letter  is  not 
given.  {Compte  rendu,  18,  1063.) 

I  have  now  completed  the  task  undertaken, 
viz.,  to  sketch  impartially  the  history  of  the 
evolution  of  the  thermometer  from  its  first  be- 
ginnings in  Italy,  through  its  crude  early  forms 
down  to  the  three  standards  now  commonly 
used  in  all  civilized  lands.  It  is  interesting  to 
note  :  First,  that  no  nation  makes  popular  use 
of  the  thermometer  designed  by  its  own  citi- 
zen. The  instrument  constructed  by  the  Ger- 
man Fahrenheit  in  the  Netherlands  is  used 
almost  exclusively  in  English-speaking  lands ; 


REAUMUR  AND  CELSIUS.  87 

that  invented  by  the  Frenchman  Reaumer 
finds  no  credit  in  France,  but  is  popular  in 
Germany ;  and  that  of  Celsius,  the  Swede, 
modified  by  Christin,  of  Lyons,  is  used  chiefly 
in  France,  Belgium,  and  Switzerland. 

Secondly,  no  one  of  the  thermometers  now 
in  use  has  exactly  the  scale  originally  devised 
by  the  person  whose  name  is  attached  to  it, 
later  and  more  perfect  methods  of  manufacture 
having  modified  the  primary  form. 

The  following  table  of  thirty-five  thermom- 
eter scales  has  been  compiled  from  many  sources, 
including  the  tables  of  Dr.  Martine  and  of  Van 
Swinden. 


1 

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O  B 


CHRONOLOGICAL  EPITOME. 


T595     Open  air-thermoscope  invented  by  Galileo. 
1611     Sanctorius  applies  Galileo's  instrument  to  the 

diagnosis  of  fevers. 
1611     Telioux'  thermoscope. 
1617     The  word  "thermoscope"  used  by  Giuseppe 

Bianconi. 

1624     The  word  ' '  thermometer ' '  used  by  Leurechon. 
1632     Water-thermoscope  invented  by  Jean  Rey. 
1641     Sealed  alcohol  thermometers  of  Ferdinand  II. 
1651     Caspar  Ens  originates  the  Drebbel  myth. 
1643     Kircher's  thermoscopes. 
1657     Differential  thermometer  of  Caspar  Schott. 

1660  Giant  thermometer  of  De  Guericke,  and  self- 
registering  thermometer. 

1 66 1  Fabri  makes  a  scale  by  dividing  the  interval 
between  the  temperature  of  snow  and  of  mid- 
summer heat. 

1664  Freezing-point  of  water  taken  as  a  fixed  point 
on  scale  by  Robert  Hooke. 

1665  Boyle  uses  aniseed  oil  to  get  fixed  point  on 
scale. 

1667     Florentine   thermometers    described    in    the 

"  Saggi." 

1670     Paris  thermometer. 
1688     Dalenc£  publishes  his  "Traitte""  and  proposes 

divers  scales. 


CHRONOLOGICAL  EPITOME.  91 

1694     Renaldini  proposes  freezing-point  and  boiling- 
point  of  water  as  fixed  points  in  scale. 

1701  Sir  Isaac  Newton's  linseed  oil  thermometer. 

1702  Amon tons'  researches. 

1709  Fahrenheit's  alcohol  thermometers. 

1714  Fahrenheit's  mercury  thermometers. 

1727  Fowler's  thermometers. 

1730  Reaumur's  thermometers. 

1733  De  Lisle 's  thermometer. 

1740  Scale  of  Du  Crest. 

1742  Scale  of  Celsius. 

1743  Christin   reverses   the   scale   of   Celsius   and 
thereby  establishes  the  ' '  Centigrade  ' '  scale. 


AUTHORITIES. 


Abbe,  Cleveland.  Ann.  Rep.  Chief  Signal  Officer  ; 
1887.  Part  II,  p.  13. 

Accademia  del  Cimento.  Saggi  di  naturali  esperi- 
enze  fatte  nell'  Accademia  del  Cimento.  1667. 

Accademia  del  Cimento.  Essays  of  Natural  Experi- 
ments made  in  the  Academic  del  Cimento.  Eng- 
lished by  Richard  Waller.  London,  1684. 

Arago,  Francois.  Compte  rendue,  Vol.  VIII,  p.  1063. 

Amontons,  Guillaume.  Me"moires  de  1' Academic 
des  sciences  de  Paris.  1702  and  1703. 

Annales  de  chimie.     Paris.  Vol.  45,  p.  354.  (1803). 

Archivio  meteorologico  centrale  italiano.  Firenze, 
1858. 

Bianconi,  Giuseppe.  Sphaera  mundi,  seu  Cosmo- 
graphia  demonstrativa.  Bononiae,  1620. 

Boerhaave,  Hermann.  A  New  Method  of  Chemis- 
try, translated  by  Peter  Shaw.  London,  1753. 
2  vols. 

Boyle,  Robert.  Works,  by  Peter  Shaw.  London, 
1725.  3  vols. 

Burckhardt,  Fritz.  Die  Erfindung  des  Thermome- 
ters und  seine  Gestaltung  im  XVII  Jahrhundert. 
Basel,  1867. 

Burckhardt,  Fritz.  Die  wichtigsten  Thermometer 
des  achzehnten  Jahrhunderts.  Basel,  1871. 


AUTHORITIES.  93 

Cajori,  Florian.     A  History  of  Physics.  New  York, 

1899. 
Cammerer,    Elias.      Operosa   thermometri    fabrica. 

Ephem.  Acad.  Nat.  Curiosa.     Francof.  Cent.  I, 

II. 
Caus,  Salomon  de.     Raisons  des  forces  mouvantes. 

Franckfort,  1615. 
Caverni,  R.     Intorno  all'  invenzione del  termometro. 

Boncompagni,   Bullettino   di   bibliografia,    XI, 

1878.  pp.  531-586. 
Caverni,  R.  Storia  delmetodo  sperimentale  in  Italia. 

Firenze,  1891.     Vol.  I. 

Celsius,  Andreas.     Vetensk.  Akad.  Handl.     Stock- 
holm, 1742. 
Clauder,    Gabriel.      Thermoscopium  noviter  inven- 

tum.     Miscell.  Acad.  Nat.  Curiosa,  Dec.  2,  A.  6. 

Jense,  1687. 
Crest,   Micheli  du.     Description  d'un  thermometre 

universal.     Paris,  1741. 
Dalence*.     Traittez  des  barometres,  thermometres  et 

notiometres  ou  hygrometres.  Amsterdam,  1688. 
De  la  Hire,  Gabriel  Philippe.     Me"moires  acad.  roy. 

sciences  de  Paris,  1706. 
Drebbel,  Cornelius.  Van  de  elementen  quinta  essen- 

tia  en  primum  mobile.     Amsterdam,  1709. 
Drebbel,  Cornelius.     Griandliche  Aumosung  von  der 

Natur  und  Eigenschaft  der  Elementen.  Franck- 

furt  am  Mayn,  1715. 

Ens,    Caspar.     Thaumaturgus   mathematicus.     Co- 
lonise Agrippse,  1651. 
Fahrenheit,  Daniel  Gabriel.     Phil.  Trans.     Vols.  30 

and  33.   1724. 


94    EVOLUTION  OF  THE  THERMOMETER. 

Favaro,   A.     Galileo  Galilei  e  lo  studio  di  Padova. 

Firenze,  1883.     Vol.  I. 
Fludd  de  Fluctibus,  Robertus.   Utriusque  cosmi  .  .  . 

historia.     Londini,  1617. 
Fludd  de  Fluctibus,   Robertus.     Philosophia  Moy- 

saica.     Londini,  1638. 

Geoffroy,  Etienne  Francois.     Phil.  Trans.     1701. 
Gerland,  E.     Das  Thermometer.     Berlin,  1885. 
Guericke,  Otto  de.     Experimenta  nova  Magdebur- 

gica  de  vacuo  spatio.     Amstelodami,  1672. 
Hales,  Stephen.     Vegetable  Statics.     London,  1727. 
Halley,  Edmund.     Phil.  Trans.     1693,  p.  650. 
Hellmann,  G.     Neudruck  No.  7.  Accademia  del  Ci- 

mento;    instrumenti  per  conoscer   1'alterazioni 

dell'  aria.     Berlin,  1897. 
Helmont,  Joh.  Bapt.  von.     Opera.     1648. 
Hermann,  Jakob.    Phoronomia.  Amstelodami,  1716. 
Hoefer,  Ferdinand.     Histoire  de  la  chimie.     Deux. 

e"d.     Paris,  1866,  2  vols. 

Hooke.  Robert.     Micrographia.    Londini,  1664. 
Lambert,  J.  H.     Pyrometrie.     Berlin,  1779. 
Kircher,   Athanasius.     Magnes,   sive  de  arte  mag- 

netica.     Ed.  II.     Colon.  Agrip.   1643. 
Le  Febure.  Nicolas.     Traicte*  de  la  chymie.     Paris, 

1660,  2  vols. 
Leurechon,    Jean.     La    recreation    mathe'maticque. 

Pont-a-Mousson,  1624. 
Libri,  Guillaume.     Histoire  des  sciences  mathe'ma- 

tiques  en  Italic.     Paris,  1838,  4  vols. 
Martine,  George.     Essays  Medical  and  Philosophi- 
cal.    London,  1740. 
Mersenne,    Marin.     Cogitata   physico-mathematica. 

Paris,  1644. 


AUTHORITIES.  95 

Member,  A.  Schriften  d.  naturf.  Gesell.  Danzig. 
N.  F.  Vol.  VII. 

Monconys,  Balthasarde.  Journal  dcs  voyages.  Paris, 
1665,  3  vols. 

Nelli,  G.  B.  C.  Vita  e  commercio  letterario  di  Gal- 
ileo Galilei.  Losanne,  1793,  2  vols. 

Newton,  Isaac.     Philos.  Trans.     1701. 

Oettingen,  A.  J.  von.  Abhandlungen  iiber  Ther- 
mometrie.  (Ostwald's  Klassiker,  No.  57).  Leip- 
zig, 1879. 

Poggendorff,  J.  C.  Geschichte  der  Physik.  Leip- 
zig, 1879. 

Porta,  Giambattista  della.  I  tre  libri  di  spiritali. 
Napoli,  1606. 

Porta,  Giambattista  della.  Pneumaticorum  libri 
tres.  1601. 

Reaumur,  Rene  Antoine  Ferchault  de.  Construc- 
tion des  thermometres.  Memoires  Acad.  roy. 
sciences,  Paris,  1730,  1731. 

Renou,  E.  Annuaire  Soc.  met.  France.  Vol.  24, 
1876. 

Reyher,  Samuel.     Pneumatica.     Hamburg,  1725. 

Rosenberger,  Ferd.  Die  Geschichte  der  Physik. 
Braunschweig,  1882,  2  vols. 

Sanctorius,  S.  De  statica  medicina  aphorismorum 
sectiones  septem.  Venetiis,  1614. 

Sanctorius,  S.  Commentaria  in  primam  Fen  primi 
libri  Avicennse.  Venetiis,  1646. 

Sanctorius,  S.  Commentaria  in  artem  medicinalem 
Galeni.  Venetiis,  1612. 

Schott,  Gaspar.  Mechanica  hydraulico-pneumatica. 
Herbipoli,  1657. 


96    EVOLUTION  OF  THE  THERMOMETER, 

Soumille,  Abbe".  Histoire  Acad.  roy.  sciences,  Paris, 
1770. 

Swinden,  J.  H.  van.  Dissertation  sur  la  comparai- 
son  des  thermometres.  Amsterdam,  1778.  . 

Verulam,  Francis  de.  The  Novum  Organon,  trans- 
lated by  G.  W.  Kitchin,  Oxford,  1855. 

Verulam,  Francis  de.  Instauratio  inagna.  Londini, 
1620. 

Viviani,  Vine.  Vita  di  Galileo  Galilei,  in  Opere  di 
Galileo.  Firenze,  1718. 

Wallis,  John.     Phil.  Trans.,  1669,  p.  1113. 

Wohlwill,  Ed.    Pogg.  Ann.  Vol.  124,  p.  163.  (1865). 

OF  T: 


INDEX. 


Accademia  del  Citnento 34 

Amontons 61 

Amontons'  pyrometer 63 

Antinori's  find , 38 

Authorities,  I,ist  of 92 

Bacon,  Chancellor 26 

Baro-thermoscopes 20 

Barnsdorff 's  scale 78 

Bergen's  scale 79 

Boerhaave,  Hermann 72 

Brisson's  scale 83 

Boyle,  Robert 41 

Caus,  Salomon  de 26 

Cartesian  divers. 33 

Castelli 18 

Celsius,  Andreas 85 

Centigrade  thermometer 86 

Christin  of  I^yons 85 

Crest,  Micheli  du 84 

Dalenc£ 50 

De  la  Hire's  thermometer 64 

De  1'Isle,  Jos.  Nicolas 84 

De  I<uc  and  I,ambert 84 

Differential  thermometer 49 

Drebbel,  Cornelius 8 

Epitome,  chronological 90 

Fabri,  Honor£ 46 

Fahrenheit,  Daniel  Gabriel 66 

Fahrenheit's  publications 69 

Ferdinand  II 32 

Florentine  thermometers 35 

Fludd,  Robert 27 

Fowler's  thermometers , 80 

Galileo,  inventor  of  the  thermometer .  14 

Geoffrey,  Etienne  Fran£ois 60 


98  INDEX. 


Guericke's  thermometers 47 

Helmont,  J.  B.  van 32 

Hermann,  Jakob 63 

Hooke,  Robert 44 

Hubin,  Sieur 52 

Huyghens,  Christian 45,  54 

Hygroscopes  of  Sanctorius 23 

Kircher,  Athanasius 31 

I,eurechon's  thermometer n 

Medicina  statica 22 

Mercurial  thermometers 53 

Mersenne,  Marin 28 

Meteorology  in  Italy 39 

Newton,  Sir  Isaac 57 

Newton's  pyrometer 58 

Porta,  Giambattista  della   .   . 10 

Reaumur,  Seigneur  de 81 

Renaldini,  Carlo 56 

Romer,  Olof 56 

Rey,  John 29 

Saggi  .    .    .   Acad.  del  Cimento 35 

Sagredo's  letters  to  Galileo 15 

Sanctorius 20 

Sarpi,  Paolo 2S 

Scales  of  Fahrenheit 74,  77 

Schott,  Caspar 49 

Scientists  of  Holland 67 

Soumille's  thermometers 83 

Stromer,  Marten 85 

Table  of  scales 88 

Telioux •    •    •  25 

Temperature  in  Iceland 76 

Thermo-barometer  of  Fahrenheit 69 

Thermometer,  first  occurrence n 

Thermoscope,  first  occurrence n 

Wolf,  Christian  von 56,  65,  71 


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